A sample of 201 children aged between 2 and 9 years with bilateral chronic otitis media with effusion (OME) were treated prospectively and at random by adenoidectomy, adenotonsillectomy, or with neither procedure. In all cases only a unilateral grommet was inserted and the contralateral unoperated ear was examined one year post-operatively for persistence or resolution of the effusion. A self-administered questionnaire was completed by the parents concerning their smoking habits. The resolution of effusion following surgery was assessed in relation to smoking by by the mother and father separately and in combination. Clearance of glue was statistically less frequent where the child's mother or where both parents smoked. This was related to the number of cigarettes smoked by the mother or both parents. The adverse effect was demonstrable whether or not adenoidectomy or adenotonsillectomy had been performed for treatment. The findings lend further support or professional and governmental opinions of a deleterious effect of passive smoke exposure on children and in this case parental smoking has been shown to have an adverse effect on the outcome of OME following surgical treatment.