Abstract: Objective To investigate the interactive effects of pet ownership and environmental tobacco smoke(ETS)on children's asthma and asthma-related symptoms.Methods Using cluster random sampling method,6 primary schools in Baise city were randomly selected,and all children in the selected schools were recruited for a survey.The information about the children's respiratory diseases,conditions of pet ownership and ETS exposure were collected with an international standard questionnaire compiled by American Thoracic Society.Results A total of 3 473 subjects completed the questionnaire with a response rate of 88.67%.The results showed that the prevalence of persistent cough,persistent phlegm,doctor-diagnosed asthma,current asthma,and current wheeze were 11.52%,6.68%,7.63%,2.04%,and 4.15%,respectively.The percentages of children exposed to pet and ETS were 17.71% and 39.48%,respectively.After adjustments for age,gender and other confounding factors,the results from multivariate unconditional logistic regression analyses showed that either pet ownership or the ETS exposure significantly increased the risk of respiratory diseases and symptoms in the children.There was a significant interaction between pet ownership and ETS exposure on persistent cough in the children(χ²=5.50,P=0.019),whereas,the combined effects of these two factors on doctor-diagnosed asthma,current asthma,and wheeze were not statistically significant(P>0.05).Conclusion The results of the study demonstrates that pet ownership and ETS exposure increases the risk of respiratory diseases and symptoms in children and there are significant interactive effects between the two factors on some respiratory diseases and symptoms.