In the gastro-intestinal tract of male Wistar rats fed a commercial diet containing 23.6 ppm dimethylamine (DMA), the concentration of DMA was highest (11.2 +/- 2.1 ppm) in the stomach and declined towards the lower regions. In contrast, the highest DMA concentration (6.6 +/- 2.5 ppm) was observed in the upper small intestine in rats fed a diet containing only 1.0 ppm DMA. DMA was absorbed in the intestines, and the disappearance curves were monoexponential. The t1/2 values for DMA in the ligated stomach, upper and lower small intestine, caecum and large intestine were 198, 8.3, 11.6, 31.5 and 11.0 min, respectively. The DMA concentration in the blood had increased to 3.0 +/- 1.0 ppm (from a pre-injection level of 0.28 +/- 0.06 ppm) 5 min after the injection of 250 micrograms DMA into the ligated upper small intestine. The disappearance curve for DMA in the blood was monoexponential and the t1/2 for the initial 15 min was 12.5 min when 250 micrograms DMA was injected into a femoral vein. The peak concentrations of DMA in the intestine and bile, respectively, were 15.6 +/- 12.6 ppm (at 15 min) and 3.7 +/- 1.9 ppm (at 30 min after the iv injection of DMA). In this 30-min period, urinary DMA increased from 17.3 +/- 9.4 to 139 +/- 23 ppm. These results show that, following ingestion, DMA is absorbed from the intestine into the blood, from which it disappears rapidly, the major part being excreted in the urine while a small proportion is excreted in the bile or secreted into the intestine, where it may be reabsorbed.