Bacteriuria detected in the screening of adult and elderly populations has been associated with an increased mortality rate, but it is not clear whether the increase is a result of the bacteriuria itself or of differences in age, concomitant disease, or both. We screened a representative sample of the elderly population of Göteborg, Sweden (n = 1966), for bacteriuria. The mean (+/- SD) age at the time of screening was 70 years +/- 2 months. The five-year mortality among women with bacteriuria was 13.4 percent, whereas that among women without bacteriuria was 9.4 percent. The nine-year mortality in the two groups of women was 23.9 and 23.3 percent, respectively (P not significant). When the women with indwelling catheters were excluded from the analysis, the five-year mortality was 9.0 and 9.2 percent, respectively. Men with bacteriuria had an increased frequency of cancer (27.3 vs. 5.8 percent at age 70; P less than 0.002) and a higher five-year mortality than the other men; however, among the men with bacteriuria but not cancer the mortality was not increased. We conclude that fatal diseases associated with bacteriuria may account for the increase in mortality among elderly patients with bacteriuria.