Reference values for four arsenic species (inorganic As(III); inorganic As(V); dimethylarsinic acid DMA; monomethylarsonic acid MMA) in urine were evaluated for 101 male persons in northern Germany (46.9 +/- 10.5 y) applying anion exchange chromatographic species separation with on-line hydride-technique atomic absorption spectrometry (between-days imprecision 6.8-10.1%; 11.0-50.0 micrograms/l; n = 30; detection limits d. l. 1; 10; 2; 2 micrograms/l). DMA was found in 88.1% of the persons (x +/- s = 7.21 +/- 9.64 micrograms/g creatinine; median 4.02 micrograms/g; 95% < 22.5 micrograms/g) followed by As(III) (11.3%; median < d. l.; 95% < 0.54 microgram/g) whereas no MMA and As(V) could be found. Seafood consumption within the last 2 days led to higher DMA levels compared to having seafood more than 6 days ago (n = 43 vs. n = 42; 10.04 +/- 11.58 vs. 3.47 +/- 3.55 micrograms/g; p < 0.01).