Tempe bongkrek was prepared from partially defatted coconut by fermentation with the mould Rhizopus oligosporus. The addition of 2% sodium chloride decreased but did not inhibit formation of bongkrek acid by Pseudomonas cocovenenans strain ITB in either coconut culture medium (CCM) or tempe bongkrek, while 2% sodium chloride or acidification of CCM to pH 4.5 with acetic acid inhibited formation of toxoflavin. Toxin formation by three strains of Ps. cocovenenans in tempe bongkrek was inhibited by the combination of 2% sodium chloride and reduction of pH to 4.5 with acetic acid. Mycelial growth of R. oligosporus was sometimes affected by toxin production by Ps. cocovenenans, but not by the addition of 2% sodium chloride and/or acidification of CCM to pH 4.5 with acetic acid.