Symptoms and signs of acute maxillary sinusitis have seldom been specifically analyzed. Since there is a gradual transition from rhinitis to sinusitis it can be expected that many symptoms are common for the two diseases. However, since sinusitis requires drainage measures and/or antibiotic treatment, both of which seldom are actual for rhinitis, the differential diagnosis is important. The present investigation confirms most of the symptoms presented previously in textbooks. However, most of these sympatoms which conventionally are supposed to indicate sinus disease were found to be just as common in radiologically normal sinuses and in sinuses with pronounced changes. The subjective or objective finding of purulent nasal secretion was more helpful in the differentiation between rhinitis and sinusitis. It appears that the patient's symptoms do not constitute a reliable diagnostic basis for the confident differentiation between the two diseases. The simplest and least discomfortable means of demonstrating sinusitis is by radiology.