Simultaneous removal of hydrogen sulfide (H2S) and trimethylamine (TMA) using a bacterial deodorant was investigated. The bacterial deodorant consisted of Thiobacillus thiooxidans JCM7814 cells and sodium citrate buffer. H2S was biologically removed by T. thiooxidans cells, which oxidized the H2S at a maximum oxidation rate of 0.84 mmol-H2S/g-cell . min in a reaction mixture based on the sodium citrate buffer. TMA was chemically removed by a neutralizing reaction with the citric acid contained in the buffer. The removability of both malodorous gases depended on the pH and the citrate concentration in the buffer. Appropriate buffer conditions for simultaneous removal of the gases were : pH range, 2.0-4.0; citrate concentration, 0.2 M. The bacterial deodorant simultaneously removed 14.0 mu l/l H2S and 25.7 mu l/l TMA over a period of 30 min in a sealed glass vessel (gas-phase volume, 3 l), in which the initial concentrations of the H2S and TMA generated were 20 and 30 mu l/l, respectively. No decrease removability in removal capability was observed over 50 test repetitions.