The absorption of bromhexine from Bromhexin tablets 8 mg, DAK has been compared with that from Bisolvon tablets 8 mg, Boehringer Ingelheim, in a two-way complete crossover study. Four tablets of each of the two bromhexine products, corresponding to a single dose of 32 mg of bromhexine hydrochloride (77.6 mumol), was administered to each of the 10 volunteers. The plasma concentration was followed over the 4-hour period following each administration. By means of Pratt's test for paired data no statistically significant difference (p greater than 0.10) between the two products was found with respect to maximum plasma concentration (89 and 84 nmol.1(-1), respectively), the times for their occurrence (1.3 and 1.0 h, respectively), and the area under the plasma concentration-time curves (140 and 132 nmol.1(-1).h, respectively). It is concluded that Bromhexin, DAK and Bisolvon are bioequivalent. Provisional pharmacokinetic data for bromhexine, after oral administration, in man were obtained. The first-pass effect and the biological half-life were estimated by combining plasma and 30 h urine data from four of the volunteers. The first-pass effect was estimated to be c. 75 per cent, the biological half-life to be c. 6 h, and c. 0.1 per cent of the dose was found as unmetabolized bromhexine in the urine. The data indicate that the pharmacokinetics of bromhexine may be described as a two-compartment open model.