The plasma concentrations of the organic nitrates (nitric acid esters) trans-2-amino-2-methyl-N-(4-nitroxycyclohexylmethyl)-propionamide (BM 12.1200) and of 4-(2-nitroxyethyl)-piperidine (BM 12.1173, CAS 129999-77-5) were determined in dog plasma by capillary gas chromatography with electron capture detection (GC-ECD). Intra- and interassay variation coefficients of the gas chromatographic analysis lay between 2.9 and 8.8%; recoveries amounted to 50-62%. Both nitric acid esters were absorbed quickly and attained maximum plasma levels within 1 h. The total bioavailability of BM 12.1200 is > 55%, and that of BM 12.1173 is 63%; their elimination half-lives are, respectively, 4.2 h and 1.3-1.4 h. Thus, BM 12.1173 and the reference substance IS-5-MN (isosorbide-5-mononitrate) show corresponding elimination half-lives. These results regarding the pharmacokinetic parameters of BM 12.1173 were confirmed by cross-over application of BM 12.1173 and IS-5-MN to Macaca Arctoides. In comparison to all species which have been treated with IS-5-MN thus far, the shortest elimination half-life (t1/2 = 0.6 h) is found in monkeys.