Budesonide has been used for a number of years as a topical nasal corticosteroid in the treatment of nasal allergy and nasal polyps. Recently, a new device for powder insufflation where no constituents or preservatives are included has been developed (Rhinocort Turbuhaler, Astra Draco AB, Sweden). The present investigation was designed in order to study the efficacy of topical budesonide powder as the only treatment of nasal polyps. A total of 126 patients entered the study. The medical history and clinical recordings included symptoms and signs, a semiquantitative test of smell and measurement of nasal expiratory peak flow index. Medication was either 200 or 400 micrograms of budesonide powder b.i.d. or placebo. After 1 month an overall assessment of treatment efficacy was made to determine whether the treatment had been a success or a failure. The results showed a statistically significant improvement of symptoms and signs in the actively treated groups. The increase in expiratory peak flow index was about 60% in the actively treated groups as opposed to 16% in the placebo group. The overall assessment of treatment efficacy showed success in about 82% of actively treated patients as opposed to about 43% in the placebo group. It is concluded that budesonide powder is useful in the treatment of nasal polyps.