The L-arabinose resistance forward mutation test (ara test), together with Ames test, was performed for evaluation of mutagenicity of the surface water samples collected from Meiliang Bay, Taihu Lake in winter.The five of the nine surface water samples were detected as mutagen positive by ara test, most of them were collected from the estuary which flow into the lake or from the edge of shore area. The same tendency was observed with the involvement of mammalian S9 metabolic activation system.The roughly, coincident results were confirmed by Ames test when the sample doses applied were enhanced to two and a half times compared with that of ara test.The data suggest that detection sensitivity of ara lest is higher if intricate environmental samples are concerned.Thus, prospect for ara test to be the primary choice is prompted when the genotoxicity screening of environmental mixtures is required.