Serum from children with chronic persistent asthma was subjected to C. pneumoniae IgG antibody determination. C. pneumoniae IgG serology suggestive of persistent infection was significantly higher in chronic persistent asthma group than in the control group. Seropositivity was significantly more in moderate and severe persistent groups than in the control subjects. There was no evidence of acute C. pneumoniae infection (IgM serology done in duplicate) in acute exacerbations.