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The hydrocyanic acid potential (HCN-p) of sorghum (Sorghum Bicolor (L.) Moench] plants is recognized as a heritable trait, but previous studies on the mode of inheritance of HCN-p have produced inconsistent results. The objective of this study was to investigate the inheritance patterns of seedling HCN-p and also of seed weight in reciprocal crosses of sorghum and sudangrass (formerly S. sudanense (Piper) Stapf). Both traits were found to be inherited quantitatively. Generation means analysis indicated that additive genetic effects were most important for both seed weight (53% of variation) and seedling HCN-p (74% of variation). A maternal effect was found for both traits in the F1 and backcross generations. No evidence of this reciprocal effect was found in the F2, suggesting that cytoplasmic inheritance was not involved. A highly positive correlation between seed weight and HCN-p was found across all entries, across both parents, and in the F1 and backcross generations. However, correlation coefficients between seed weight and seedling HCN-p for individual entries, the pooled F2's, or within types of seed parents in the F1 or backcross generations were generally nonsignificant. It was concluded that seed weight per se does not have a large effect on seedling HCN-p.