The aim of this study was to determine the frequency and specificity of HLA-A and B antibodies in multiparous mothers in the Malaysian population. 1,100 maternal serum samples obtained during normal childbirth were screened against a panel of 100 lymphocytes with known HLA antigen types for HLA antibodies by the complement dependent lymphocyte microcytotoxicity dye exclusion test. From the total number of 1,100 samples of maternal serum that were screened for HLA antibodies only 205 specimens (18.6%) tested positive for antibodies. The percentage of maternal sera which contained HLA-B specificities (10.6%) were significantly higher than those which contained HLA-A specificities (3.0%). Sixty maternal serum samples (5.5%) had high enough titres to be utilised as tissue typing reagents. Thirty nine maternal serum samples (3.5%) contained monospecific HLA antibodies. In this study the most common monospecific HLA antibodies characterised included the following specificities: A2, B5, B17 and B40. Malaysian multiparous mothers of gravida 3, 4 and 5 had a higher frequency for producing HLA-antibodies.