An analbuminemic congenic strain of rats originating from ACI (ACI-alb) rats was established. The rats were found to be highly susceptible to induction of urinary bladder cancer by N-butyl-N-(4-hydroxy-butyl)nitrosamine. Bladder cancers were observed in all male ACI-alb and normal ACI rats treated with the compound, but the average weight of the bladder including tumors was more in ACI-alb rats than in ACI rats (0.63 +/- 0.24 g and 0.18 +/- 0.05 g, respectively; ratio, 3.5:1).