Condensation of Cbz-Asp and PheOMe catalyzed by a neutral protease from Vibrio sp. T1800 (Vimelysin : VLN) was studied. VLN showed a relatively higher catalytic activity of condensation and an apparently larger yield after 3 h or 24 h, in comparison with thermolysin (TLN), especially at lower pH and temperatures. VLN showed higher solvent-tolerance than TLN. TLhe apparent highest yield (25%) was obtained in 30% DMSO by using VLN; under similar conditions, TLN gave only about a half of this value. The rate of the condensation reaction per mole of enzyme (v/[E](o)) in DMSO 50% at 37 degrees C and pH 6.5 was 0.16 s(-1) for VLN and 0.047 s(-1) for TLN. In 30% ethanol VLN showed more than three-fold peptide yield than TLN after 5 h reaction.