The histological types of lung cancer in Hong Kong Chinese in both sexes are presented. When the 1981 WHO Classification is used instead of the 1967 WHO Classification, more than half of the large cell carcinoma is retyped into the adenocarcinoma group. The proportion of large cell carcinoma thus decreases from 14.7% to 6.9% in the male and from 10.0% to 4.4% in the female. Compared to the 1948-1962 report from the same Department, there is a shift of the peak age distribution from the 6th decade to the 7th decade. Compared to the 1960-1972 report from the same Department, there is a significant increase in the relative frequency of adenocarcinoma in both sexes, from 15.6% to 25.8% in the male and 34.3% to 49.6% in the female. Adenocarcinoma continues to be the most common histological type in females and it is becoming the commonest type in males. It is also found in the present series that in the male, the proportion of adenocarcinoma decreases with increasing age, from 60% in the third decade to 26.6% in the eighth decade. In spite of the high female lung cancer mortality rate and therefore low male:female ratio of about 2:1, there is a tendency for this ratio to increase over the years. It is speculated that factors other than active cigarette smoking may be responsible for the peculiar and changing histological pattern and the female predominance in lung cancer in Hong Kong Chinese.