Despite the promutagenic/procarcinogenic potential, polycyclic aromatic amines are widely spread in the environment. Biotransformation of the polycyclic aromatic amine 2-aminofluorene (2-AF) was proved in mammals and higher plants. The algal cell/microbe coincubation assay is an additional system that complemented those proved in mammals and higher plants, useful for detection and conversion of environmental promutagens, mainly in aquatic environments. The unicellular green algae may be a good activating system in coincubation assays in that the algal cells exist as a natural system. To increase the effectiveness of this metabolizing system, different modifications of the standard experimental procedure were conducted. Algae can accumulate and metabolize promutagenic pollutants, some of which may differ from those activated by the animal microsome metabolizing system (S9 mix) and by the plant cell/microbe coincubation assay. 2-AF was activated in the algal cell/ microbe coincubation assay in which wild-type Chlamydomonas reinhardtii cells were used as an activating system and the bacteria Salmonella typhimurium TA98, YG1024, and yeast Saccharomyces cerevisiae D7 as the genetic indicator organisms. It was converted to the mutagenic product(s) for the strain YG1024, but the strain TA98 did not exhibit any increase in the mutant yield of His+ revertants. Consequently, metabolites from 2-AF are substrates for O-acetyltransferase. A direct comparison of algal 2-AF activation with mammalian activation system (S9 mix) proved the higher activity of mammalian microsome system (S9 mix). After the combination of both activation systems, a slight synergetic effect was found. Although the genetic endpoints induced by 2-AF using both modifications of the algal cell/S. cerevisiae coincubation assay and those obtained in intact yeast cells were similar at the equitoxic concentrations, 2-AF activation by the algal supernatant slightly increased the genetic endpoints studied.