Due to its various uses, Cr contamination has become widespread in a diverse array of environments. The present study was carried out during 2007-2008 to investigate the accumulation potential of metals (Cr, Cu, Fe, Mn, Ni and Zn) and metalloid (As) by green (CA) and blue green (BGA) microalgae growing naturally in selected Cr-contaminated sites in districts Unnao and Kanpur (Uttar Pradesh, India). This investigation is a preliminary work to identify suitable native microalgae for biomonitoring and phytoremediation purposes. A total of 22 CA and 11 BCA were encountered in three seasons (summer, rainy and winter). Among these, the accumulation potential was evaluated in high biomass producing strains of BGA (three) and GA (nine). The maximum accumulation of Cr was shown by Phormedium bohneri (8550 mu g g(-1) dw) followed by Oscillatoria tenuis (7354 mu g g(-1) dw), Chlamydomonas angulosa (5325 mu g g(-1) dw), Ulothrix tenuissima (4564 mu g g(-1) dw), and Oscillatoria nigra (1862 mu g g(-1) dw); all of which demonstrated a transfer factor of >10% for Cr. The results also indicate that the phytoplankton diversity was modified by Cr pollution. BCA represented the dominant community where Cr concentration was higher (11.84 and 2.27 mg L-1) (r = 0.695), whereas CA showed negative correlation with respect to Cr concentration (r = -0.567). In conclusion, different algal species were able to grow in Cr-contaminated sites and to accumulate significant amounts of Cr with a high transfer factor. (C) 2009 Elsevier B.V. All rights reserved.