Sugar catabolism of alkaliphilic bacilli was investigated to reveal their catabolic characteristics. Four bacilli were cultured in the presence of various 1% (w/v) sugars and related compounds such as sugar alcohols, and the catabolites formed were analyzed. All alkaliphiles produced acetic acid (4.5-5 g/l at the maximum) while formic acid was produced by only one of the strains. In contrast to neutrophilic bacilli, acetoin, butanediol or ethanol was not detected. Moderate amounts of isobutyric, isovaleric, alpha-oxoisovaleric, alpha-oxo-beta-methylvaleric, alpha-oxoisocaproic and phenylacetic acids were generated with three of the alkaliphiles. High pH and/or buffer concentration tends to favour formation of acids. The studied alkaliphiles are compared among each other and with neutrophilic bacilli.