A pilot study of azithromycin treatment following percutaneous coronary revascularization procedures was performed to assess safety and the effect of azithromycin treatment on anti-Chlamydia pneumoniae antibody titres. Patients were randomized to a 1 month course of azithromycin (total dose of 8.0 g) or placebo. Safety and compliance were assessed at 2 and 4 weeks and serological testing was performed on samples obtained at enrolment and at 6 months post-enrolment. Azithromycin was well tolerated at this dose. No effect of treatment on antibody titres was demonstrated. These results support further clinical trials to assess the effect of azithromycin treatment on cardiovascular disease outcomes.