Red cell acid phosphatase polymorphism was studied by starch gel electrophoresis in 70 b-thalassemia patients and in 310 healthy Greeks. Our results gave the following gene frequencies: b-thalassemia patients: pa 0.321, pb 0.643, pc 0.036; healthy Greeks: pa 0.302, pb 0.653, pc 0.045. No statistically significant differences were found between the two groups.