There has been much emphasis on breeding for increased sweetpotato storage root yields, but less on the dry matter yield, and its inheritance. High dry matter content (DMC) is associated with consumer preferences, and is important for processing industry. This study was conducted to determine the type of gene action controlling DMC and to assess GxE interaction effect on DMC in sweetpotato. Five parental clones varying in DMC have been hand-crossed in a half-diallel design to generate 10 families. After scarification, seeds were raised in seedboxes in a screenhouse at Namulonge, Uganda. Ten genotypes of each family were planted in a trial at Namulonge (swamp and upland environments) and Serere in a randomized complete block design, with two replications, during October 2009 and March 2010.