Twenty patients receiving a variety of emetogenic cytotoxics (including cisplatin in 5) were given a single i.v. infusion of 40 micrograms kg-1 of BRL43694 (as the hydrochloride salt) in successive groups of 3-4 patients between 0-6 hours after chemotherapy. Eleven patients were completely protected from vomiting; 9 had mild to moderate nausea and vomiting, but none severe enough to require alternative anti-emetic 'rescue'. In 4 of the patients in whom BRL43694 was delayed until 4-6 h after chemotherapy, vomiting had already begun; in each case immediate termination of vomiting occurred when BRL43694 was infused. No adverse effects attributable to the anti-emetic were observed. Mean pharmacokinetic parameters in 14 patients in whom plasma assay data are available were: Maximum observed concentration = 30.7 ng ml-1; terminal phase half-life = 8.96 h; total body clearance = 0.376 (1 h-1) kg-1; apparent volume of distribution = 2.85 l kg-1. This study shows BRL43694 to be an effective and well tolerated anti-emetic. Further studies aimed at defining an optimal dose and schedule for use against the most emetogenic cytotoxics are in progress.