Prognostic factors in 411 patients with small cell lung carcinoma have been retrospectively analysed. Univariate analysis of continuous variables showed that prognosis was worse with deteriorating performance status, extensive disease, positive bone scan, increasing age, elevated total white cell count, alkaline phosphatase, lactate dehydrogenase, and decreased serum chloride and albumin. Low serum sodium was less clearly associated with poor survival. Cox multivariate regression showed that performance status, disease extent, age and raised lactate dehydrogenase and white cell count were independent prognostic factors. When disease extent was excluded from analysis, performance status, age, total white cell count, lowered serum chloride and raised lactate dehydrogenase were significant independent prognostic variables.