Levels of the tumour markers neurone specific enolase (NSE), lactate dehydrogenase (LDH), chromogranin A (ChrA) and carcinoembryonic antigen (CEA) were measured in serum taken at presentation and during treatment, remission and relapse from 154 patients who received chemotherapy for small cell lung cancer at a single centre over a 6 year period. This evidence concerns the gene HRAS and small cell lung carcinoma.