We tested the hypothesis that supplemental dietary vitamin D3 could be used to improve tenderness of pork. On the basis of elevation of blood calcium concentration and constant feed intake, we determined that 500,000 IU daily for three days before slaughter was the optimal dosage. This dosage resulted in no improvement in pork tenderness as based on two commonly used tenderness measurements. Several other measures of pork quality were determined, but only one was affected by dietary vitamin D3. Carcasses from the vitamin D3 supplemented pigs had more carcass shrinkage than did those of nonsupplemented pigs. Thus, this initial study indicated that supplemental dietary vitamin D3 does not improve pork tenderness and other measures of pork quality. The principal objective of this experiment was to test whether supplemental dietary vitamin D3 improved tenderness of pork. Two commonly used methods of assay for tenderness were used to complete the objective. Both methods of assay demonstrated that supplemental dietary vitamin D3 did not improve tenderness. Perhaps other doses of vitamin D3 or other feeding schedules of the vitamin D3 may result in an improvement in pork tenderness as occurred for beef. Future research is needed to address these issues.