We describe a method for obtaining nondistorted and reproducible transferrin (TF) typing from liquid semen and semen stains. Isoelectric focusing of TF isoproteins on polyacrylamide gel (IEF-PAGE, pH 4 to 6.5) was accomplished using a 0.5 mm thick gel. The separated isoproteins were then visualized by immunoblotting with TF-specific antibody. Pretreatment of semen samples with neuraminidase enhanced the TF band resolution. The method was reliable, sensitive and simple, with a high resolution. When maintained at room temperature, laboratory-prepared semen stains were TF-typable for up to at least 50 weeks. The TF types in semen stains were correlated with the types found in the corresponding blood and urine samples. TF typing could therefore provide an additional discriminant characteristic in the forensic examination of semen stains. An evaluation of TF typing by IEF-PAGE and immunoblotting was also performed on casework samples submitted to our laboratory.