We determined the inheritance of host resistance to MDMV for the inter se crosses among 10 inbred lines of corn (Zea mays L.). Trials were conducted in 2 years at two locations. Diallel analyses indicated that the general combining ability and the specific combining ability mean squares were statistically significant, but that the gca mean square was substantially larger than the sca mean square. Differences in MDM scores were noted between years and locations. Our results agree rather well with previous studies based on diallel analysis and generation mean analysis. Previous studies indicated that disease symptoms are expressed more intensely when competition from johnsongrass (Sorghum halepense L.) Pers., as well as from other forms of environmental stress, becomes extreme. Also, host reaction to MDMV is confounded with hybrid vigor. We conclude that these sources of bias would be minimized by evaluating F1 hybrids.