Two field experiments were carried out  during 1995 and 1996 to evaluate 18 white maize populations (3 local and 15 exotics) for their differences in drought tolerance under 5 moisture regimes in order to identify the best ones for future use in breeding programs. The 5 moisture regimes included:  well watering (WW), stress at pre-flowering (BF), stress at  flowering (FS), stress at post-flowering (AF) and severe stress (SS) at both flowering and post-flowering stages. A split-plot design with 3 replicates was used, where main plots were alloted for the moisture regimes, while sub-plots were for the maize populations. Fourteen traits were analyzed.                 Drought stress caused significant reductions in grain yield and most of the studied traits, while days to 50 silking, anthesis-silking  interval (ASI), leaf/air temperature, percentage of barrin stalks and leaf rolling traits were increased. Flowering stage was the most sensetive period with respect to grain yield. The local cultivar Giza-2 and the two exotic populations (DTP-1and DTP-2) bred for drought tolerance by CIMMYT were the most drought tolerant genotypes at all growth stages, based on their absolute, relative and potential yields. Drought tolerance of maize appears to be specific for a certain growth stage, but genotypes could be bred for tolerance at more than one growth stage. The most drought tolerant genotypes had a shorter ASI, lower leaf/air temperature , higher number of ears/plant, earlier flowering, lower leaf rolling and lower percentage of barren stalks, than those of the most susceptible genotypes.