DISEASE CHARACTERISTICS: Histologically confirmed malignant solid tumor at original diagnosis Refractory to standard treatment or no curative therapy available No CNS tumor No bone marrow metastases (for less heavily pretreated stratum only)

PATIENT CHARACTERISTICS: Age: At least 365 days to 17 years Performance status: Karnofsky 50-100% (for patients older than 10 years) Lansky 50-100% (for patients 10 years and younger) Life expectancy: At least 8 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 (transfusion independent) Hemoglobin at least 8.0 g/dL (RBC transfusion allowed) Hepatic: Bilirubin no greater than normal SGPT no greater than 2.5 times normal Albumin at least 2 g/dL Alkaline phosphatase normal Gamma glutamyl transferase less than 2.5 times normal Renal: Creatinine no greater than 1.5 times normal OR Creatinine clearance or GFR at least lower limit of normal Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception Creatine phosphokinase less than 2 times normal No uncontrolled infection Seizure disorder allowed if well controlled on anticonvulsants No CNS toxicity greater than grade II

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 1 week since prior biologic therapy and recovered At least 1 week since prior growth factor therapy At least 6 months since prior peripheral blood stem cell transplantation and no evidence of graft-vs-host disease For less heavily pretreated stratum: No prior peripheral blood stem cell transplantation Chemotherapy: At least 4 weeks since prior myelosuppressive chemotherapy (6 weeks for nitrosoureas) and recovered No prior ecteinascidin 743 For less heavily pretreated stratum: No more than 2 prior chemotherapy regimens Endocrine therapy: Not specified Radiotherapy: At least 2 weeks since prior local palliative radiotherapy (small port) At least 6 weeks since prior substantial bone marrow radiotherapy At least 6 months since prior craniospinal radiotherapy or radiotherapy to 50% or greater of pelvis For less heavily pretreated stratum: No prior craniospinal irradiation of 18Gy or greater No prior irradiation to greater than 50% of pelvis Recovered from toxic effects of prior radiotherapy Surgery: Not specified Other: No concurrent foods or medication that interferes with P-450 metabolism Anticonvulsants allowed