Twelve inoperable lung cancer patients were treated with a combination chemotherapy of cisplatinum (CDDP) and etoposide (VP16), as a continuous infusion for 5 days, every 21 days, and with a daily oral administration of GaCl3. Dosages of CDDP and VP16 were adapted in order to obtain an area under the curve (AUC) of 80,000 micrograms l-1.h for plasma total platinum and of 200 mumol.l-1 h for plasma VP16 during each 120 h infusion. GaCl3 was given at the dosage of 400 mg/24h from the time of diagnosis at least until the evaluation after 3 courses of chemotherapy. An objective response was observed in 5 non small cell (NSCLC) lung cancer patients (group 1) and 3 small cell (SCLC) lung cancer patients (group 2). In the other 4 patients with a NSCLC no partial response was noted (group 3). No significant difference in area under the curve (AUC) was noted between the 3 groups, either for plasma total platinum (group 1 = 89,598 +/- 20,843 micrograms l-1.h; group 2 = 88,081 +/- 15,431 micrograms l-1.h; group 3 = 83,820 +/- 13,455 micrograms l-1.h), or for VP16 (group 1 = 227 +/- 41 mumol.l-1 h; group 2 = 217 +/- 29 mumol.l-1.h and group 3 = 211 +/- 30 mumol.l-1.h). The maximal plasma Ga concentrations were 244 +/- 34 micrograms/l in group 1, 112 +/- 57 micrograms/l in group 3 (p less than 0.005) and 243 +/- 132 micrograms/l in group 2. It was then decided to increase the dose of GaCl3 in the further non-responding patients. In 6 responders, 3 additional courses of this combination chemotherapy could have been given without major toxicity, allowing a much more important decrease in the tumor volume in 4 of them. This schedule of treatment should permit the chemotherapy to continue for longer than 6 courses, in order to improve the survival time.