Mass/heat transfer measurements are made using the naphthalene sublimation method in a square internal passage where one wall has a single dimple. Four types of dimple shapes are studied: square, triangular, circular, and teardrop. Sherwood numbers are obtained both inside and around the dimples. Measurements are made at a Reynolds number of 21,000. In addition, computations are performed for the same dimple geometries, and with the same flow conditions as in the experiments. Flow patterns for the four dimples are identified and heat transfer distributions for each dimple are obtained. The computational results are compared with the experimental data and show satisfactory agreement. Both the experimental and numerical results suggest that the teardrop dimple has the highest heat /mass transfer among the four dimple shapes studied.