Age-adjusted mortality from lung cancer rose rapidly in both males and females in Hong Kong from 1960-1972. The relative frequency of epidermoid carcinoma increased in male bronchial biopsies but not in lung biopsies, resections, or autopsies; there was a decline in small-cell anaplastic carcinoma. In both males and females the ratio of Kreyberg Group I (epidermoid and small-cell anaplastic) to Group II (adenocarcinoma and carcinoid) tumours did not increase, despite an 80% rise in mortality from lung cancer. Adenocarcinoma was the most common type in females, despite the high mortality from lung cancer. It is speculated that cigarette smoking might produce a different pattern of histological types among Hong Kong Chinese, or that additional aetiological factors may be operating there