Point mutations in N, K and H RAS have been found in adverse haematological malignancies. The background frequency of RAS mutations in the normal population has yet to be determined. Here we report the results of a screen for RAS mutations from normal individuals.DNA from peripheral blood or bone marrow from 115 haematologically normal individuals was screened for point mutations in N, K and H RAS, at amino acid positions 12, 13 and 61. The screening was done using polymerase chain reaction and oligonucleotide hybridisation and candidate mutations were subsequently confirmed by cloning and sequencing.Point mutations were identified in DNA from two of the 115 individuals. Both mutations resulted in an amino acid substitution at position 12 in H RAS. Both individuals with detectable H RAS mutations remain haematologically normal.