The histology pattern of lung cancer in Los Angeles County was reviewed for a 10-year period, 1972-81. In men, the total lung cancer incidence has been fairly constant, but there has been a shift in the histology pattern with an increase in adenocarcinoma and a decrease in "other" cell type (i.e., carcinoma not otherwise specified, large-cell and undifferentiated tumors). This changing histology pattern may be partly due to changes in diagnostic standards and practices. With the assumption that these changes are comparable in men and women, the "true" annual rate of change was estimated for each lung cancer cell type in women. All lung cancer types have increased in women; of the cell types squamous cell carcinoma, small-cell carcinoma, and adenocarcinoma, small-cell carcinoma showed the largest rate of annual increase and adenocarcinoma, the smallest.