• Clinical sexual characteristics evaluated using Tanner staging (pubic hair and genital development in males, pubic hair and breast development in females). [ Time Frame: Weeks 4, 8, 12, 24, 36, 48, then every 6 months until end of treatment; post-treatment every 6 months until puberty, then every 12 months for 5 yrs ] [ Designated as safety issue: No ]
• Height and growth rate based on stadiometer assessment at office visit or self-reported by subject on Questionnaire [ Time Frame: Weeks 4, 8, 12, 24, 36, 48, then every 6 months until end of treatment; post-treatment every 6 months until puberty, then every 12 months until 21 yrs old, and Final Post-treatment Questionnaire at adulthood. ] [ Designated as safety issue: No ]

• Hormone laboratory test results (peak stimulated and basal LH and FSH, stimulated and basal estradiol (girls) or testosterone (boys) [ Time Frame: Weeks 4, 8, 12, 24, 36, 48, and then every 6 months until end of treatment; post-treatment every 6 months until puberty, then basal levels every 12 months for 5 yrs ] [ Designated as safety issue: No ]
• Bone Age for ratio of bone age to chronological age and predicted mature height. [ Time Frame: Weeks 24 and 48 then every 12 months until end of treatment; post-treatment every 6 months until puberty, then every 12 months for 5 yrs. ] [ Designated as safety issue: No ]
• Reproductive Function: Assessed by menstrual cyclicity; ability to become pregnant; use of birth control or other hormonal treatment; number and outcome of pregnancies. [ Time Frame: During all of treatment (spotting or bleeding assessment) and post treatment follow-up (menses assessment ), Final Post-treatment Questionnaire and/or Follow-up Visit when patient reaches adulthood ] [ Designated as safety issue: Yes ]
• Incidence of Ovarian Cysts: Assessed by history of ovarian cysts and abdominal ultrasound ovarian findings [ Time Frame: Final Post-treatment Questionnaire and/or Follow-up Visit ultrasound when patient reaches adulthood ] [ Designated as safety issue: Yes ]

• Hormone laboratory test results (LH suppression). [ Time Frame: Weeks 4, 8, 12, 24, 36, 48, and then every 6 months until end of treatment, and end of treatment day. ] [ Designated as safety issue: No ]
• Ratio of change in bone age to the change in chronological age. [ Time Frame: Weeks 24 and 48 then every 12 months until end of treatment and end of treatment day. ] [ Designated as safety issue: No ]
• Predicted mature height. [ Time Frame: Weeks 24 and 48, then every 12 months until end of treatment, and end of treatment day. ] [ Designated as safety issue: No ]

The purpose of this study is to determine if leuprolide acetate is safe and effective in treating children with Central Precocious Puberty, and to assess long term effects of leuprolide acetate treatment after therapy is discontinued.

This study will use hormonal and physical measurements to determine if leuprolide acetate is safe and effective for treating children with central precocious puberty. The dose of leuprolide acetate for depot suspension will start at 300 mcg/kg (minimum 7.5 mg), given in the muscle every 28 days, with incremental adjustments of 3.75 mg (minimum 7.5 mg and maximum 15 mg) if needed based on clinical and laboratory measurements. Approximately 10 study sites will participate in a total of 50 or more subjects. This study includes a Prestudy Period and once enrolled, patients will be followed at least every 12 weeks for the first year and then, every 6 months thereafter until the drug is discontinued (until the NDA is approved or the IND is withdrawn, or until treatment is discontinued at the discretion of the physician or parent.) At the treatment visits, gonadotropins/sex steroid levels, safety labs, physical exam, bone age by radiograph, height, weight, and Tanner stage will be assessed. In addition, this protocol will capture long-term outcome data on reproductive function, final height and incidence of ovarian cysts as these children reach adulthood. Following discontinuation of therapy (puberty), patients will be assessed for height, weight, Tanner staging, bone age, gonadotropin / sex steroid levels, ultrasound, menstrual history for girls and urine sample for presence of sperm for boys at specified visits for 5 years until puberty is reached, then annually until 21 years of age for height and reproductive potential. To collect final information on adult height, reproductive potential and ovarian cysts, patients will be contacted and asked to return for a final clinic visit and complete a questionnaire, have a final height and weight measurement, and females will undergo an abdominal ultrasound to assess ovarian cysts. Following this data collection, the study will be concluded.

Inclusion Criteria:

• Clinical diagnosis of isosexual central precocious puberty with onset of Tanner scores of Stage II for breast or pubic hair earlier than age 8.0 years in girls or Stage II for pubic hair or genitalia earlier than 9.0 years in boys.
• Confirmation of diagnosis by a pubertal response to a GnRH stimulation test (LH > 10 U/L at baseline).
• Chronological age less than 9.0 years in girls or less than 10.0 years in boys at time of first dosing.
• Bone age advanced at least one year beyond the chronological age at entry into the study.
• The condition may be idiopathic or secondary to another lesion. If secondary, therapy of the primary condition will have been undertaken and stabilized.
• No evidence of abnormal pituitary, adrenal, thyroid and gonadal function except for premature secretion of gonadotropins.

Exclusion Criteria:

• Irradiation to the central nervous system.
• Prior therapy with medroxyprogesterone acetate and/or with any GnRH analog (including prior treatment with daily subcutaneous and depot formulations of leuprolide acetate).