Objective. N-methyl-2-pyrrolidone (NMP) is a strong and selective organic solvent with an extensive and increasing use. It has been reported to be a compound that is toxic to the reproductive system. The aim of this study was to evaluate toxicokinetics parameters for NMP and its metabolites, 5-hydroxy-N-methyl-2- pyrrolidone (5-HNMP), N-methylsuccinimide (MSI) and 2-hydroxy-N-methylsuccinimide (2-HMSI), and to develop a method for biological monitoring of NMP exposure that uses 2-HMSI as a biomarker. Methods. Six healthy, male volunteers were exposed to NMP in an exposure chamber for 8h at concentrations of 10, 25 and 50mg/m3. In addition, three of the subjects were exposed a second time at 50mg/m3. Air levels were monitored by Amberlite XAD-7 sampling and gas chromatography (GC) analysis. Levels of NMP and the metabolites in plasma and urine were analysed by GC or GC with mass spectrometry detection. Results. The concentration of 2-HMSI in plasma and urine rose during exposure and reached a peak approximately 15h after the end of exposure. It then decayed according to a one-compartment model with a half-time of about 18h. There were very close correlations between the NMP air levels, on the one hand, and concentrations of 2-HMSI in plasma (r=0.98) and creatinine-adjusted urinary 2-HMSI levels (r=0.96), on the other. The renal clearances were 0.13, 1.4, 0.12 and 1.2l/h for NMP, 5-HNMP, MSI and 2-HMSI, respectively. The total clearances were 11.4, 3.2, 8.5 and 1.1l/h for NMP, 5-HNMP, MSI and 2-HMSI, respectively. The apparent volumes of distribution were 41, 28, 120 and 28l for NMP, 5-HNMP, MSI and 2-HMSI, respectively. Conclusions. Toxicokinetics parameters for NMP, 5-HNMP, MSI and 2-HMSI have been estimated. Furthermore, 2-HMSI is applicable as a biomarker of exposure to NMP, and the levels in plasma and urine may be used to indicate an exposure over three days.