OBJECTIVE Major changes in the incidence of the most common histological types of lung and bronchus cancer have been observed around the world. Herein we report the overall incidence, stage at diagnosis and overall mortality of lung and bronchus cancer in Puerto Rico, and the incidence of the different histologic types. METHODS Aggregate lung and bronchus cancer data from 1987 to 2003 were obtained from the Puerto Rico Central Cancer Registry. Incidence and mortality rates were age-standardized by the direct method to the 2000 standard population of the United States. For the incidence (overall, by histologic type, and by sex), and mortality we calculated the annual percent change (APC) using the Joinpoint Regression Program. RESULTS There were 9,886 cases of lung and bronchus cancer (6,772 men, 3,114 women), for an overall age-adjusted incidence of 18.8 per 100,000. The incidence decreased significantly for the whole group, falling from 18.9 per 100,000 in 1987 to 17.1 in 2003 (APC: -0.74, p < 0.05); for men, incidence decreased from 28.1 per 100,000 to 24.4 (APC: -1.02, p < 0.05) over the same period of time. The mortality rate has decreased overall (APC: -0.62, p < 0.05) and in men (APC: -0.71, p < 0.05). Squamous cell carcinoma was the most common histologic type in 1987, but it decreased from 6.2 per 100,000 in 1987 to 3.5 in 2003 (APC: -3.86, p < 0.05), while adenocarcinoma increased from 3.7 per 100,000 to 4.6 (APC: +1.51, p < 0.05). CONCLUSIONS In Puerto Rico, over the period of 1987 to 2003, squamous cell carcinoma of the lung and bronchus decreased, while adenocarcinoma increased. As of 1999, the most common type of lung and bronchus cancer is adenocarcinoma. Both the incidence and the mortality of lung and bronchus cancer decreased for men but not for women.