Human milk and plasma samples were obtained from five healthy nursing mothers who were taking nefopam hydrochloride (60 mg four-hourly) for post-episiotomy pain. Concentrations of nefopam were quantified in milk and plasma paired samples, taken daily from birth for 5 days, by a specific paired-ion reverse phase h.p.l.c. method. Although nefopam was present in human milk in an equivalent concentration to plasma (milk: plasma ratio 1.2 +/- 0.7, mean +/- s.d.), the likely infant exposure was less than 0.05 mg kg-1 day-1 which, on a body weight basis, would be less than 3% of the maternal dose.