Quantification of Bdellovibrio-and-like organisms (BALOs) by microbial culturing has a number of substantial drawbacks. Therefore a quantitative PCR (qPCR) assay was designed for the cultureindependent enumeration of the Bdellovibrionaceae. After optimization, the dynamic range of the qPCR assay was assessed, the specificity was evaluated and a comparison with quantitative microbial culturing was made. To evaluate the suitability of the qPCR assay for analysing environmental samples, fresh water samples were investigated by microbial culturing and by the qPCR assay. The results revealed a substantial difference between the two techniques and indicate that most Bdellovibrionaceae cells are left undetected in environmental samples when only current microbial culturing techniques are used. The application of this new technique is therefore likely to confirm the hitherto underestimated sizes and roles of predatory bacterial populations in nature.