There have been many reports of benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) being used as recreational drugs which have been widely marketed in the form of 'party pills' since the late 1990's. However, there is no information currently available describing the pharmacokinetics of these drugs in humans. Human plasma concentrations of BZP were measured in blood and urine samples taken from healthy adults (n=7) over 24h following a 200mg oral dose of BZP. Plasma concentrations of BZP were found to peak at 262 ng/mL (C(max)) and 75min (T(max)). Plasma concentrations of the major metabolites of BZP, 4-OH BZP and 3-OH BZP, were found to peak at 7 ng/mL (at 60 min) and 13 ng/mL (at 75 min) respectively. The elimination half-life (t(1/2)) for BZP was found to be 5.5h. Clearance (Cl/F) was found to be 99L/h. The results of this study indicate that BZP may be detectable in plasma for up to 30 h following an oral dose. Additionally, several urinary metabolites can be detected.