BACKGROUND HLA-DR typing was generally performed by serology before. HLA-DRB1 typing can be achieved by polymerase chain reaction amplification with sequence specific primers (PCR-SSP). METHODS In this study, primers for "low-resolution" HLA-DR typing by PCR-SSP were synthesized upon our request by a company in Taiwan. Twenty-eight DNA samples from international standardized DNA Reference Panel and 20 DNA samples with known serological typing were used as control. We conducted HLA-DR PCR-SSP typing on 18 samples from 6 true paternity trios, 16 samples from 8 true duos, 27 from 9 false trios, and 8 from 4 false duos. These DNAs from disputed paternity families had been previously tested for the parentage using polymerase chain reaction (PCR)-amplified short tandem repeat (STR) analysis. RESULTS No false positive nor false negative results were obtained in typing 28 positive control DNA samples from international standardized DNA Reference Panel for HLA Class II. Among the 20 DNA samples typed by microlymphocytotoxicity technique, the discordant typing results between HLA-DR PCR-SSP typing and serological typing were found in 3 (15%). In the family of true paternity, HLA-DR typing could not exclude any of alleged fathers and the pattern of inheritance was consistent with autosomal codominant. By HLA-DR typing alone, paternity in 2 alleged fathers out of 9 false trios and 2 alleged fathers out of 4 false duos could not be excluded. CONCLUSIONS Precise HLA-DR typing can be achieved by PCR-SSP analysis. Economic considerations preclude HLA-DR typing in routine parentage tests where STR typing is performed first.