We have studied the duration distribution of the gamma-ray bursts of t
he first BATSE catalog. We find a bimodality in the distribution, whic
h separates GRBs into two classes: short events (<2 s) and longer ones
(>2 s). Both sets are distributed isotropically and inhomogeneously i
n the sky. We find that their durations are anticorrelated with their
spectral hardness ratios: short GRBs are predominantly harder, and lon
ger ones tend to be softer. Our results provide a first GRB classifica
tion scheme based on a combination of the GRB temporal and spectral pr
operties.