This study focused on ideal methods of detecting C. parvum oocysts which give low detection limits, specific and sensitive detection in concentraded samples, and differentiation of viable from non-viable oocysts; are usable by a water treatment facility and provide quantitative results within a few hours. Potential useful methods are continuous flow centrifugation, rel-time TaqMan PCR, cell culture inoculation followed by PCR of DNA extration, and FISH.