Drought is a major factor limiting maize (Zea mays L.) yield in much of the world. The need to breed maize cultivars with improved drought tolerance is apparent. This study compared two maize populations, ZM601 and ZM607 for drought tolerance during flowering, the most drought-vulnerable period for the maize plant. Cultivar ZM601 had been improved through recurrent selection for two cycles for drought tolerance at flowering plus one cycle under rainfed (random) drought stress, while ZM607 had been improved for high yield for three cycles under favorable growing conditions. A set of 143 random S1 lines from ZM601 was compared with 94 from ZM607 at two drought stressed and one well-watered environment for yield and secondary traits. The results did not show much difference in drought tolerance between ZM601 and ZM607. Differences between population means for grain yield, anthesis-silking interval (ASI), and number of ears per plant (EPP) were small. Frequency distributions for ASI and leaf rolling were different for the two populations. However, ZM601 had more lines with shorter ASI and less leaf rolling as compared to ZM607. Broad sense heritability of ASI was larger,while that of grain yield smaller, and the correlation between ASI and grain yield was larger at drought-stressed compared to unstressed sites. Absence of large differences in grain yield between ZM601 and ZM607 lines was attributed to little effect of the selection completed prior to this evaluation, to genetic similarities of the two populations prior to selection, and to large genotype-by-environment interaction between Mexico, where drought screening was conducted, and Zimbabwe, where this evaluation was conducted. Results confirmed the value of ASI (measured at drought-stressed sites) as an indirect selection criterion for improving grain yield under drought stress conditions. Key Words: Anthesis, heritability, recurrent selection, secondary traits, Zea mays, Zimbabwe Resume La secheresse est un facteur majeur limitant la production du mais (Zea mays) dans le monde. La necessite de croiser les varietes de mais avec des varietes resistantes a la secheresse est apparente. Cette etude a compare deux populations, ZM 601 et ZM 607 pour la tolerance a la secheresse pendant la periode de floraison, la periode la plus vulnerable pour le mais. La variete ZM 601 a ete ameliore a travers la selection recurrente pour deux cycles pour la tolerance a la secheresse a la floraison en plus d'un cycle pendant la periode pluvieuse (au hazard) stress de secheresse, alors que ZM 607 a ete ameliore pour rendement eleve pour trois cycles dans des conditions favorables. Un ensemble de 143 races S pris au hazard de ZM 601 etait compare avec 94 races de ZM 607 a stress deux secheresses et un environnement bien arose pour le rendement et les traits secondaire. Les resultats n'a pas montre de difference significative dans la tolerance a la secheresse entre ZM 601 et 607. Les differences entre moyennes des populations concernant le rendement en grains, l'interval d'anthesis-silking, et le nombre d'oeillet par plante etait petit. La distribution de frequence pour ASI et roulage des feuilles etait differente pour les deux populations. Cependant, ZM 601 avait plus des lignes avec des couts ASI et moins de roulage des feuilles compare au ZM 607. L'heritabilite de ASI etait tres large, celle de rendement en grains faible, et la correlation entre ASI et le rendement en grains etait elevee pour les sites stresses par la secheresse compares aux sites non stresses. L'absence des differences larges dans le rendement en grains entre les races ZM 601 et 607 etait attribue au faible effet de la selection faite avant l'evaluation, aux similarites genetiques de deux populations avant la selection, et a la grande interaction genotype-environnement entre le Mexique ou depistage a ete conduit et le Zimbabwe ou l'evaluation a ete conduite. Les resultats ont confirme la valeur de ASI mesuree comme un critere de selection indirect pour l'amelioration dans les conditions de stress de la secheresse. Mots Cles: Anthesis, heritabilite, selection recurrente, traits secondaires, Zea mays, Zimbabwe (Af Crop Sci J 2003 Vol 11 No 3 pp151-162)