Recently, anticipation of renal failure, i.e. earlier onset of end-stage renal disease in successive generations, has been reported in autosomal dominant polycystic kidney disease. In order to evaluate differences in length of time in reaching end-stage renal disease, we examined 55 families with accurate information about renal death. In 12 families the average difference between the age at renal death in 17 parent-offspring pairs was 7.7 years (range from -5 to 22 years). This value was significantly greater than zero (P = 0.0004). Thus, a substantial decrease in the age at renal death in the offspring as compared with the parent has been observed in this group of families.