Analyses of relapse in small cell lung cancer (SCLC) were performed in 443 evaluable patients included in two multicenter trials. The time to first progression mainly depended on best response to therapy. Nearly all patients with no change (NC) suffered from progression within 6 months. In patients with partial remission (PR), progression occurred within 12 months in nearly all cases. If complete remission (CR) was achieved, no relapse was seen within the first 6 months after the onset of treatment. Between the 6th and 8th month a slowly increase and after the 8th month a rapid increase of relapse was noticed. In the majority of patients with limited disease relapse was localized in the area of the primary tumor, whereas in patients with extensive disease relapse mostly was due to the development of distant metastases. Of the 443 patients, 35 achieved 2-year survival (8%). Main prognostic factors for the achievement of 2-year survival were extent of disease and sex. Patients with distant metastases and CR had a poor chance of achieving a 2-year survival, while patients without distant metastases and CR had a 30% chance. Females with limited disease and a Karnofsky score of 70% or more had a 40% chance of achieving 2-year survival, the corresponding probability for males was less than 10%. Because of the high frequency of relapse in SCLC, the stabilization of best response has to be considered as a main objective in therapy. In our opinion, two different strategies may be useful in order to achieve higher 2-year survival rates: a) periodic controls and renewal of therapy as soon as possible after relapse has occurred or b) reinduction therapy in intervals of about 8 weeks or more in order to delay or prevent the development of relapse. To find out if one of these strategies is superior to the other, is one of the objectives of our new randomized trial in SCLC.