To evaluate the extent of the association between hyperhomocysteinaemia and chronic ischaemic heart disease.Unmatched, case-control (1:3) study.Pintores Health Centre, Area 10, Primary Care, Madrid, Spain.Patients of the health centre over 35 with chronic ischaemic heart disease or without it.Consecutive, non-randomized sample. Analysis of cases and controls with chi2 test and odds ratio (OR). The quantitative variables were analysed with the Student's t test.The 76.32% (87/114) of cases had 2 or more cardiovascular risk factors versus 33.56% (99/265) in the control group (P or =15 micromol/L) between cases (28.95%, 33/114) and controls (12.88%, 38/295) was significant (P=.0001), with an association between hyperhomocysteinaemia and chronic ischaemic heart disease (OR=2.76; 95% CI, 1.62-4.68). This association increased (OR=3.26; 95% CI, 2.07-5.13) when hyperhomocysteinaemia was taken as > or =12 micromol/L, with a significant difference of 27% (95% CI, 16.59-37.41) (P or =15 micromol/L was significantly associated (OR=2.76) with chronic ischaemic heart disease. This association was greater (OR=3.26) when hyperhomocysteinaemia was taken as > or =12 micromol/L.