The pharmacokinetics of 2 beta, 16 beta-bis-(4'-dimethyl-1'-piperazino)-3 alpha, 17 beta-diacetoxy-5 alpha-androstane dibromide (pipecurium bromide, Arduan), a new non-depolarizing neuromuscular blocking agent, was studied in surgical patients. Plasma concentration-time curves of pipecurium bromide were evaluated by fitting the data to a bi-exponential equation. The average half-lives were T 1/2 alpha = 4.1 +/- 1.4 (n = 8) and T 1/2 beta = 44 +/- 7 (n = 8) min. The pharmacokinetic parameters of pipecurium bromide were found as follows: apparent distribution volume V beta = 261 +/- 28 (n = 8) ml/kg, plasma clearance Cl = 320 +/- 55 (n = 8) ml/min. The microconstants of two-compartment open models were also calculated.