Idiopathic annular submitral left ventricular aneurysm has been described mainly in young Africans living in tropical countries. Association with peripartum cardiomyopathy has been previously pointed out. The purpose of this report is to describe 3 patients with idiopathic annular submitral left ventricular aneurysm identified in a series 50 patients with peripartum cardiomyopathy in Niamey, Republic of Niger. Anti-Chlamydia pneumoniae antibody status was determined in all 50 patients using the micro-immunofluorescence technique that differentiates IgG, IgA and IgM antibodies. Findings showed that all 3 patients with annular submitral left ventricular aneurysm had significantly elevated plasma IgG and IgA anti-Chlamydia pneumoniae antibody levels at the time of diagnosis. In one patient analysis of 2 samples collected 3 months apart indicated chronic elevation with exceptionally high IgG antibody levels (1/2048e). These previously unreported data suggest a possible link between Chlamydia pneumoniae and development of peripartum cardiomyopathy and annular submitral left ventricular aneurysm. This possibility is supported by recent evidence that specific IgA anti-Chlamydia pneumoniae antibodies may be predictive of aortic abdominal aneurysms.