Forty-seven haemophilia A patients from 43 pedigrees and 34 haemophilia B patients from 31 pedigrees were screened for the presence of mutations by Southern blotting using factor VIII and IX cDNA and genomic DNA probes. Three deletions and two restriction site variants were detected among 47 haemophilia A patients and one deletion and two restriction site variants were detected in 34 haemophilia B patients. Overall, the frequency of mutations in haemophilia A was 10.6%; the frequency of deletions was 6.4% and that of point mutations was 4.2%. In haemophilia B, the frequency of mutations detected was 9%; deletions 9% and point mutations 6%. The present report, the first from India, shows that like other earlier published reports from Europe and the United States, mutations in haemophilia are heterogeneous, and that RFLP using Southern blotting did not detect most of the mutations in this disorder and is an insensitive and inefficient procedure.