The time-trend and geographical distribution of mesothelioma of the peritoneum during the years 1967-82 in England and Wales have been studied from the Mesothelioma Register held by the Medical Division of the Health and Safety Executive. Over the 16-year period the annual number of cases registered rose from about 15-20 to about 30-50. Although the number occurring in men was double that in women, the trend was similar for both sexes. There is likely to be some further increase before any improvement due to the recent diminished usage of asbestos is seen. Local Authority areas with raised rates have been identified, and the geographical pattern is similar to that of the distribution of the asbestos-using industry in the past. In both sexes there are high registration rates on the east side of London but, in contrast to mesothelioma of the pleura, a concentration of cases among men in the major ports where shipbuilding and ship repairing were carried out is not so apparent.