Sniff-induced negative pressure in the middle ear space has recently been demonstrated in patients with the retraction type of middle ear disease. In the present study pressure recordings were performed in a consecutive series of 50 children treated with ventilating tubes for otitis media with effusion. It was found that a majority of the patients were able to induce negative pressure in the middle ear by sniffing. The ability to equalize negative pressure was found to be poor. These findings suggest a causal relationship between sniff-induced negative pressure in the middle ear space and the development of middle ear effusion.