Maize Streak virus (MSV) disease is a major disease in many parts of Africa, and is the most important viral pathogen of maize in Kenya. A study was conducted in 2004 to evaluate the agronomic performance and maize streak virus (MSV) resistance of maize ( Zea mays
L.) three-way crosses developed in Kenya. Twenty hybrids and one check were grown under normal conditions in a randomized complete block design, in two replications at Embu, 1540 masl; and Muguga, 2093 masl). In a parallel trial in Muguga, hybrids were also evaluated in two replications under artificial inoculation with MSV. The analyses of variance combined across environments showed significant differences (P<0.05) among genotypes for grain yield, days to 50% pollen shed, days to mid-silk and ear height. Genotype x environment interaction was significant (P<0.01) for grain yield and days to mid-silk, indicating some hybrids were more adapted in some environments. Grain yield for MU03-025 (10.04 t ha-1
) was significantly better (P<0.05) than the check, H513 (7.53t ha-1
). In the disease inoculated experiment, the best hybrids for disease resistance were MU03-012 and MU03-006 (score of 1.75), while H513 had a mean score of >3.0. The highest yielding hybrid under disease inoculation, MU03-026 showed yield gain of 5.2 t ha-1
above that of H513. The results indicate adoption of disease resistant hybrids would result in a higher maize yields in the mid-altitude areas of Kenya.