OBJECTIVE To study possible associations between coronary heart disease and serological evidence of persistent infection with Helicobacter pylori, Chlamydia pneumoniae, or cytomegalovirus.

DESIGN Population based, case–control study, nested within a randomised trial.

SETTING Five general practices in Bedfordshire, UK.

INDIVIDUALS 288 patients with incident or prevalent coronary heart disease and 704 age and sex matched controls.

RESULTS High concentrations of serum IgG antibodies to H pylori were present in 54% of casesv 46% of controls, with corresponding results for C pneumoniae seropositivity (33% v 33%), and cytomegalovirus seropositivity (40% v 31%). After adjustments for age, sex, smoking, indicators of socioeconomic status, and standard risk factors, the odds ratios (95% confidence intervals) for coronary heart disease of seropositivity to these agents were: 1.28 (0.93 to 1.75) for H pylori, 0.95 (0.66 to 1.36) for C pneumoniae, and 1.40 (0.96 to 2.05) for cytomegalovirus.

CONCLUSIONS There is no good evidence of strong associations between coronary heart disease and serological markers of persistent infection withH pylori,C pneumoniae, or cytomegalovirus. To determine the existence of moderate associations between these agents and disease, however, larger scale studies will be needed that can keep residual confounders to a minimum.