title: Erratum.
abstract: In the abstract of the report "L-Isoleucine and L-leucine: Tumor promoters of bladder cancer in rats" by Y. Nishio et al. (21 Feb., p. 843), the third sentence should have read, "Results of 40- to 60-week carcinogenesis experiments in which N-butyl-N-(4- hydroxybutyl)nitrosamine was used as an initiator demonstrate that L-isoleucine and L-leucine promote bladder cancer in rats."