Cancer-specific survival prospects for rectal carcinoma in a series of 1306 patients managed from 1950 to 1979 by one surgeon worsened from 1970 to 1979. The prognosis was worse for all patients treated operatively from 1970 to 1979 compared with 1960 to 1969 (P less than 0.03). After potentially curative resection, survival was worse from 1970 to 1979 compared with 1950 to 1959 (P less than 0.02) and 1960 to 1969 (P less than 0.01), respectively; the corresponding five-year survivals were 72.5 percent, 72.3 percent, and 61.5 percent. The curative resection rate for the three decades was similar (66 to 70 percent). An increase in the incidence of Dukes' Stage C tumors from 23.3 percent to 32.3 percent (P less than 0.01) explains, at least partly, the decreased survival. The worsened survival prospects were not accounted for by changes in referral pattern, tumor site, or in the proportion of sphincter-saving resections performed. The worsening was paradoxically paralleled by earlier symptomatic presentation (P less than 0.001). Analyses of other Australian data are required to test the hypothesis that the worsened survival prospects are consequent to altered tumor biologic aggressiveness, possibly related to differences in the causal factors operating over the 30-year study period.