Inclusion Criteria:Patients are included in the study if all of the following criteria are met:

1. Written informed consent is obtained.
2. The patient is English-speaking and 18 through 64 years of age inclusive.
3. The patient meets the DSM-IV criteria for PTSD as determined by the MINI and psychiatric evaluation.
4. The patient is currently taking a medication for PTSD for ≥ 12 weeks and remains symptomatic for insomnia
5. The patient has failed to respond to at least two of the following sleeping agents (there must be at least two drug classes failed): true benzodiazepines hypnotics (temazepam), non-benzodiazepine GABA modulating hypnotics (zaleplon dosed x2 or zolpidem, an antihistamine (trazadone or mirtazapine), or an atypical antipsychotic (olanzapine or quetiapine).
6. The patient is in good health as determined by a medical and psychiatric history, medical examination, lab tests.
7. Women must be of nonchildbearing potential [i.e., postmenopausal, be surgically sterile (hysterectomy or tubal ligation)] or must meet all of the following conditions: using a reliable, medically accepted form of contraception for at least 60 days before the baseline visit, and agree to continue such use throughout the duration of the study and for 30 days after the final dose of study drug. Reliable forms of contraception include oral, implanted, or injected contraceptives; intrauterine devices in place for at least 3 months; and adequate barrier methods in conjunction with spermicide (abstinence is considered an acceptable contraceptive regimen). Women must be given a pregnancy test (ßHCG), unless they are at least 2 years postmenopausal or surgically sterile, and the results of the test must be negative.

8. The patient must be willing and able to comply with study restrictions and to remain at the clinic for the required duration during the study period, and willing to return to the clinic for the follow-up evaluation as specified in this protocol.

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Exclusion Criteria:Patients are excluded from participating in this study if 1 or more of the following criteria are met:

1. Have a primary Axis I or II psychiatric condition outside of PTSD
2. The patient is a significant risk of suicide
3. The patient has a history of substance dependence (except nicotine) ever
4. The patient has a history of substance abuse in the last 5 years
5. The patient has any serious, unresolved or unstable medical and/or psychiatric condition (treated or untreated) which makes Xyrem treatment risky. The inborn error of metabolism succinic semialdehyde dehydrogenase deficiency is contraindicated Uncontrolled hypertension, heart failure are relative contraindications due to Xyrem's high salt content
6. The patient has previously participated in any clinical study with Xyrem or treated with Xyrem.
7. The patient is a pregnant or lactating woman (women becoming pregnant during the study will be withdrawn from the study).
8. The patient has used an investigational drug within 1 month before the screening visit or is participating in a concurrent clinical trial.
9. The patient has any disorder that may interfere with drug absorption, distribution, metabolism, or excretion (including gastrointestinal surgery) or have an explanable medical condition causing insomnia

(k) The patient is unlikely to comply with the study protocol, be unreliable in providing ratings, or is unsuitable for any reason, as judged by the investigator.

(l) The patient has a clinically significant deviation from normal in the physical examination.

(m) The patient has a responsibility that would require them to wake up and perform within 4 hours of a Xyrem dose (n) The patient refuses to cease use of sleeping pills (o) The patient has been diagnosed with sleep apnea (we will clinically prescreen for this and check on initial EEG).

(p) If the patient lives alone, they will need to agree to being called by a member of the study team to assess the subject's well being on the morning after the first ingestion of study drug and on the morning after any dose increase to monitor for excess sedation, sleepwalking, etc. (q) If the patient lives with children less than 6 years of age, they will not be allowed in the study.

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