This paper reports the results of a stratified, randomized trial of monthly intradermal injections of Glaxo BCG in addition to conventional therapy (surgery, radiotherapy or no treatment) in a consecutive series of 75 men with confirmed bronchial carcinoma. BCG treatment did not significantly prolong survival but had consistenly more effect in prolonging the period in good general condition and in "acceptable" clinical condition. These were significantly prolonged among the BCG patients (all histopathologies) treated with a full course of radiotherapy (p = 0.01, p = 0.005) and among the 43 patients with squamous carcinoma after adjustment for treatment and general prognostic factors (ratio of observed to expected deaths (O/E) for BCG 0.65, P = 0.025). There was a tendency for BCG patients with oat cell carcinoma to survive less well than controls (O/E for BCG 1.40 not significant). Within comparable groups of patients with squamous carcinoma the delay in decline of general condition was accompanied by reduced weight loss.