The aim of the present study was to evaluate pharmacological and toxicological properties of potassium thiophene-3-trifluoroborate (RBF(3)K). The acute effect of RBF(3)K was evaluated on mice. To this end, mice received a single dose of RBF(3)K (25, 50, and 100 mg/kg, by oral route, p.o.) and after 72 hrs, blood, liver, and kidney samples were collected. delta-Aminolevulinate dehydratase, catalase and glutathione-S-transferase activities, thiobarbituric acid-reactive substances and vitamin C levels, as well as plasma aspartate and alanine aminotransferase activities and creatinine levels were determined. Hepatic and renal lipid peroxidation levels in treated mice did not differ from those in control mice. No significant differences between treated and control mice were detected in hepatic and renal delta-aminolevulinate dehydratase activity. Aspartate and alanine aminotransferase activities as well as urea and creatinine levels were similar among the groups. In contrast, results obtained from in vivo experiments revealed that RBF(3)K, orally administered, reduced peritoneovisceral pain induced by acetic acid administered i.p. Doses of 1, 5, 10, 25, 50, and 100 mg/kg of RBF(3)K were assessed in the antinociceptive investigation and the effect was significantly different than control groups from 5 mg/kg. It was observed that alpha(2-)adrenergic and serotonergic, but not opioidergic, receptors appear to be involved in orally administered RBF(3)K. Mice treated with RBF(3)K did not reveal any motor impairment in the open field. This is a promising compound for more detailed pharmacological studies involving organotrifluoroborate compounds.