The aim of this study was to determine the seroprevalence of toxocariasis in adult asthmatics and to assess its relationship with risk factors. A total of 124 asthmatic and 60 control group subjects were included in the study. Of the asthmatic patients, 61 (49.2%) were atopic and 63 non-atopic (50.8%). The anti-Toxocara IgG (Toxocoro IgG CELISA Cellabs, Australia) positivity rate for all asthmatic cases was 9.7%. There was no significant difference between the asthmatic cases and the control group regarding anti-Toxocoro IgG positivity (P > 0.05). When risk factors were analyzed, there was A statistically significant difference between the control group subjects and patients with non-atopic asthma and also between the atopic asthmatic patients and the patients with non-atopic asthma regarding pets being under veterinary control (P < 0.05). The percentages of those who had their pets defecate indoors were 0, 15 and 8.6%, respectively, for the control subjects, patients with non-atopic asthma and those with atopic asthma. There was a statistically significant difference when the control group subjects were compared to the patients with atopic asthma (P < 0.05). (c) 2006 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.