Abstract:The aim of this trial was to assess whether early crossover induction chemotherapy would improve the complete response rate in patients with small cell lung carcinoma. Tumour markers were defined in all 48 patients at diagnosis. The patients were reassessed after three and six cycles of chemotherapy and classified as having either complete, partial or non response of tumour on each occasion.Initial induction therapy consisted of cyclophosphamide, vincristine and adriamycin (T1). The therapy of the patients with no tumour response was changed to a regimen (T2) consisting of VP16‐213, procarbazine, CCNU and high dose methotrexate with folinic acid rescue. The patients with partial tumour response were randomised to receive either T1 or T2, while patients with complete tumour response continued with T1.In those patients classified initially as having partial tumour response, crossover chemotherapy did not improve tumour response or survival. Similarly, in patients with no tumour response there was not an acceptable improvement.We conclude that non cross resistant crossover chemotherapy using these drug regimens confers no added benefit when compared with continuing the initial therap