Aims: To assess two real-time PCR methods (the Riviere and Qvarnstrom assays) for environmental Acanthamoeba. Methods and Results: DNA extracted from Acanthamoeba castellanii taken from water and biofilms of cooling towers was analysed by the Riviere and Qvarnstrom assays. To quantify environmental Acanthamoeba, the calibration curves (DNA quantity vs cell number) were constructed with samples spiked with A. castellanii. The calibration curves for both quantitative PCR assays showed low variation (coefficient of variation of C-t < 5 center dot 7%) and high linearity (R2 >= 0 center dot 99) over six orders of magnitudes with detection limit of three cells per water sample. DNA quantity determined by Qvarnstrom assay was equivalent between trophozoites and cysts (P = 0 center dot 49), whereas a significant difference was observed with Riviere assay (P < 0 center dot 0001). Riviere assay failed to detect Acanthamoeba in 21% (15/71) of the environmental samples which were positively detected by Qvarnstrom assay, while one sample (1 center dot 4%) was shown positive by Riviere assay but negative by Qvarnstrom assay. Moreover, Acanthamoeba counts by Qvarnstrom assay were greater than those by Riviere assay (P < 0 center dot 0001). Conclusions: Qvarnstrom assay performs better than Riviere assay for detection and quantification of Acanthamoeba in anthropogenic water and biofilms. Significance and Impact of the Study: Qvarnstrom assay may significantly contribute to a better knowledge about the distribution and abundance of Acanthamoeba in environments.