Technical Abstract: Gene flow between cultivated sorghum [Sorghum bicolor subsp. bicolor (L.) Moench] and its wild relative, shattercane [S. bicolor subsp. drummondii (Nees ex Steud) de Wet & Harlan], may contribute to changes in fitness and the potential invasiveness of shattercane. In order to assess the initial potential for such gene introgression into shattercane, we crossed a common parental line of sorghum (RTx430) to an inbred line of shattercane to produce F1 hybrids and measured their fitness relative to both parents. Experiments were conducted in chambers to compare germination at various temperatures. Field experiments were conducted to compare emergence, phenology, growth, and fecundity. Germination experiments showed that shattercane and the F1 were partially dormant at low temperature. Cultivated sorghum and the F1 exhibited greater mortality at elevated temperature than shattercane. The F1 was taller and produced more biomass compared to either parent in the field, but the F1 leaf area index (LAI) was intermediate between sorghum and shattercane. The greater height and LAI of the F1 suggests that it may be more competitive for light than either parent. Seed mass of the F1 was intermediate between sorghum and shattercane. Number of seeds per F1 panicle was similar to shattercane and much greater than cultivated sorghum. Glumes did not completely encapsulate the F1 seed, as is the case in shattercane, which may reduce overwintering survival of the F1 in soil. Considering all data, our results indicate that the relative fitness of shattercane x cultivated sorghum F1 hybrids may be greater than the wild shattercane parent.