The aim of this study was to investigate a possible time trend and status quo of dipropylheptylphthalate (DPHP) exposure. DPHP is used as a substitute of other high molecular weight phthalates in high temperature applications (e.g cable wires, roofing membranes, etc.). DPHP was selected in the cooperation project between the German Federal Ministry for Environment (BMU) and the German Chemical Industry Association (VCI) due to its listing as High Production Volume (HPV) chemical in the European Union. The BMU-VCI project establishes new human biomonitoring methods and biomarkers for fifty emerging substances. 300 urine samples (24-hour voids) from the German Environmental Specimen Bank were analyzed for three specific, secondary oxidized DPHP metabolites (with hydroxyl, oxo and carboxy modifications of the alkyl side chain). Urine samples were collected in the years 1999, 2003, 2006, 2009 and 2012, 60 samples per year, from 30 male and 30 female volunteers (age: 21-29 years). The samples were analyzed by liquid/liquid extraction followed by GC-HRMS, which enabled us to distinguish between DPHP and Di-iso-decyl phthalate (DiDP) metabolites. The limit of quantification was between 0.15 µg/l and 0.3 µg/l, depending on the metabolite. All samples were blinded before analysis. DPHP metabolites were not detected in the years 1999-2006. Thereafter, detection rates increased from 3.3% in 2009 to 21.7% in 2012. As expected, mono-oxo-propylheptyl phthalate (oxo-MPHP) was the most abundant metabolite, with concentrations between <LOQ and 0.96 µg/l. The daily DPHP intake was calculated via oxo-MPHP with a maximum of 0.32 µg/kg bodyweight/day. Our results show that DPHP exposure has reached the general German population. However, exposure to DPHP is considerably lower than for other high molecular weight phthalates. Future measurements will enable us to monitor the development of DPHP exposure and advise risk management steps, if warranted. Abstract: N-Methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP) are multi-purpose organic solvents in industry. Both are developmental and teratogenic toxicants in rodents. NMP is classified as a REACh substance of very high concern. Because of their toxicological profile and their broad application resulting in a possible exposure of the general population, NMP and NEP were chosen as target substances for the cooperation project between the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB) and the German Chemical Industry Association (VCI) aiming to establish human biomonitoring (HBM) methods for "new" substances of interest. NMP and NEP are metabolized to 5-hydroxy-N-alkyl-2-pyrrolidones (5-HNMP, 5-HNEP) and 2-hydroxy-N-alkylsuccinimides (2-HMSI, 2-HESI). We analyzed these specific metabolites in 24-hour urine samples from the German Environmental Specimen Bank. For this purpose, 20 randomly selected samples collected in 1996 and in 2012, respectively, were analyzed by a sensitive and specific GC-MS/MS method with isotope dilution quantification. We detected NMP metabolites in 100% and NEP metabolites in 95% of all samples. Despite the considerable differences in the elimination half-times of the alkyl pyrrolidone metabolites, the correlations between the metabolites were rather strong (NMP: r=0.51; NEP: r=0.67). An exposure determined through one metabolite is thus confirmed by the other metabolite. Median NMP metabolite levels were comparable between 1996 (5-HNMP 50 µg/L, 2-HMSI 46 µg/L) and 2012 (5-HNMP 39 µg/L, 2-HMSI 41 µg/L). Surprisingly, urinary levels of NEP metabolites were approx. 10 times higher in 1996 (5-HNEP 14 µg/L, 2-HESI 42 µg/L) as compared to 2012 (5-HNEP ~1 µg/L, 2-HESI 5 µg/L). We would have expected a reverse trend for NEP since NEP has only recently been introduced into the market as a substitute for NMP. The sources of past and present exposures to NMP and NEP warrant further investigations.