Ten previously untreated patients with gastric cancer were treated with etoposide, 120 mg/m2 intravenously (i.v.) on days 4, 5, and 6, Adriamycin, 20 mg/m2 i.v. on days 1 and 7, and cisplatin, 40 mg/m2 i.v. on days 2 and 8 (EAP). Etoposide, 240 mg/m2 on days 4, 5, and 6, was administered orally instead of intravenously in alternating cycles, and pharmacokinetic studies were performed in those who had previously undergone gastrectomy or who had tumor infiltrating the stomach to determine oral bioavailability. Nine patients had advanced measurable gastric cancer, and one patient had an elevated carcinoembryonic antigen after surgery for synchronous gastric and colon cancer. The median age was 54 years (range 38-69), and the median Eastern Cooperative Oncology Group (ECOG) performance status was 2 (range 0-3). Nine of 10 patients had poorly differentiated adenocarcinoma. Twenty-four cycles were administered to 10 patients, and hematologic data were available for 23 courses. ECOG grade 4 neutropenia and thrombocytopenia developed in 19 (83%) and 8 (53%) courses, respectively. Thirteen courses (54%) were complicated by fever requiring parenteral antibiotics. Two patients (20%) died due to neutropenic sepsis. The profound myelotoxicity observed in our study prompted us to terminate the investigation prior to completing accrual. The oral bioavailability of etoposide was 21% and 36% in the two patients who had had prior gastrectomy.(ABSTRACT TRUNCATED AT 250 WORDS)