Mucosal thickening is commonly seen on X-rays of the paranasal sinuses taken in the ENT department. This sometimes leads to a sinus washout, which is clear, even though the X-rays were strongly suggestive of disease. This paper examines the prevalence of sinus X-ray anomalies in a general population, having facial X-rays for conditions other than possible sinus disease. The study suggests that up to 50 per cent of the so-called normal population may have sinus X-ray appearances consistent with sinus disease, and this may partly explain clear returns on sinus washout.