This report demonstrates the formation and characterization of sonochemically prepared bovine serum albumin (BSA)-Gemzar (Gemcitabine) microspheres and shows their increased anticancer activity compared to pristine Gemzar. The amount of loaded Gemzar was determined by light absorption measurements. The BSA-Gemzar composite was analyzed and characterized by optical microscopy and scanning electron microscopy. The release kinetics of Gemzar from the proteinaceous microspheres was tested. The BSA-Gemzar composite was examined for its anticancer activity (in vitro) in renal cancer cells (RCC, 786-O cells) using [(3)H]thymidine incorporation assays. It was found that the influence of the Gemzar-loaded microspheres on the cancer cells was significantly greater than that of an equimolar concentration of pristine Gemzar.