Toxocariasis is a common worldwide infection. Asthma, considered to be one of the most common chronic diseases, is a serious global health problem. Toxocara may be a possible etiologic agent of asthma. The aim of this study was to investigate whether there is an association between adult asthma and Toxocara sero-prevalence. Fifty three adult patients with asthma participated in the study. All patients had an age of disease onset of 20 years or older. Blood samples were tested for the presence of Toxocara antibodies using enzyme-linked immunosorbent assay (ELISA).