This work is focussed on assessing the potentialities of Lemna minor (L) for the treatment of reactive dyes polluted wastewaters and investigating the possibility of bioremoval performance stimulation by adding triacontanol hormone to the cultures. In the vast literature describing removal of reactive dyes, considering the lack of reports using of common duckweed in wastewater treatment apparently due to the inadequate efficiency. In the present study, the experiments showed that 1 mg l(-1) triacontanol stimulated duckweed growth. The effect of different dye types (Reactive Orange 14, Reactive Red 120, Reactive Black 5, Brilliant Blue R, and Reactive Brilliant Blue R) onto duckweed growth was tested. Plants grew at most in media with Brilliant Blue R. The highest biomass, in terms of frond number (87 +/- 1.5) were accompanied with 59.6% maximum dye removal were found in samples containing 2.5 mg l(-1) initial Brilliant Blue R and 1 mg l(-1) triacontanol, indicating hormonal stimulation of both activities. The results presented here that L. minor (L) could be used effectively to treat wastewaters containing dye. (C) 2010 Elsevier B.V. All rights reserved.