A total of 96 patients (74 males and 22 females) with ischaemic heart disease (IHD) who presented at a hospital in north India for cardiac bypass surgery, percutaneous coronary angioplasty or unstable angina were investigated for Lewis blood group phenotypes. A hundred and four normal healthy blood donors matched for age and sex served as controls. Lewis blood group typing was carried out on red cells using saline haemagglutination technique in a test tube with monoclonal antisera. 29.1 per cent of IHD patients had Le(a-b-) phenotype compared to 9.6 per cent of controls (P < 0.01). The relative risk of IHD for Le(a-b-) phenotype was found to be highly significant (risk = 3.87). We conclude that there is an increased frequency of Le(a-b-) phenotype among Indian patients with IHD.