The intranasal distribution from an aqueous pump spray has been assessed in 13 normal subjects, using insoluble Teflon particles labelled with 99Tcm which were intended to simulate a suspension of drug particles. Three different combinations of metered volume and spray cone angle were compared. The main deposition of particles was in the anterior, non-ciliated, part of the nose, but some particles also penetrated more posteriorly into the main nasal passages and were cleared subsequently to the nasopharynx. No particles were detected in the lungs. With a single puff of 100 microliters volume, 46.5 +/- 4.4 (mean +/- SEM)% of the spray was retained in the anterior part of the nose after 30 minutes, but this was increased to 57.1 +/- 4.5% (P less than 0.05) with two puffs of 50 microliters. The latter were deposited over a significantly (P less than 0.05) smaller area in the nasal cavity. There was a trend towards lower particle retention and a greater area of deposition when the spray cone angle was decreased from 60 degrees to 35 degrees. These results indicate that the drug particles released from nasal pump sprays are distributed both to ciliated and non-ciliated zones, and that the choice of metered volume and possibly spray cone angle may play a role in determining the amount which penetrates to the main nasal passages.