During 1981-1986 the Edinburgh Lung Cancer Group prespectively registered 3560 new patients with lung cancer of whom only 48 (1.3%) were aged less than 45 years. When compared with 3512 older patients aged more than 45 years, a similar proportion of young patients were female (17/48; 35% vs. 28% of the older patients) and had equally advanced disease (30/48; 62% vs. 58% in stage III). Slightly more young patients were in better Karnofsky performance status groups (28/48; 59% vs. 45%, score > 80) and duration of symptoms was considerably shorter (median 45 vs. 93 days); only three of the younger patients were non-smokers. A pathological diagnosis was obtained more often in young patients (47/48; 98% vs. 81%). The commonest cell type was small cell (16/48; 34% vs. 24%) with 10/48 adenocarcinoma (20% vs. 13%) and less squamous carcinoma (11/48; 23% vs. 48%). Although only 12/48 young patients (25% vs. 19%) underwent surgical resection, six of these were still alive after 5 years (50% vs. 30% in older patients). More young patients received chemotherapy either alone (14) or combined with radiotherapy (6)--42% vs. 16% in older patients. There were no long-term survivors and the median survival was 8 months in 13 patients with small cell and only 4 months in seven with non-small cell carcinoma.