Four muskmelon (Cucumis melo L.) genotypes, MR-12, Hara Madhu, Punjab Sunehri, and Punjab Hybrid were evaluated for their multiple disease reaction to downy mildew, powdery mildew, and muskmelon mosaic, and for their yield and quality performance. Among the open pollinated varieties, MR-12 contracted the least intensity of the diseases and thus registered the least multiple disease score. It therefore recorded the highest marketable fruit yield and desirable fruit quality. The occurrence of downy mildew had a positive and significant correlation with days to first picking during 1990 as well as with its pooled value over three years and a negative and significant correlation with vitamin C content during 1989. The occurrence of powdery mildew had a positive and significant correlation with pooled days to first picking. The incidence of viral mosaic exhibited a negative and significant correlation with pooled average total soluble solids (TSS) and vitamin C content during 1990.