Combining ability and heterosis for yield, maturity, and plant traits in bush muskmelon (Cucumis melo L.) were estimated through the use of a 6-parent diallel evaluated in 1981 at Excelsior, Minn. and at Santa Paula, Calif. The variance of GCA was greater than that of SCA for all traits. Minnesota 266 was the best general combiner for yield weight characteristics. Minnesota 101 was exceptional for GCA in those traits associated with earliness, and U.C. Perlita Bush and U.F. G508 combined well for main crop yield. Correlations between the performance of parental lines and the average of their hybrids were consistently positive and often significant. Favorable heterosis over the midparent was found for all traits but days to first fruit. Favorable heterosis over the superior parent was found for plant health and all yield traits except total number of fruit per plant. In a 3 × 10 design II at Excelsior, estimates of additive variance exceeded those of dominance variance in general, providing for moderately high heritability estimates (40–70%) for most traits.