A system for the rapid detection of microbial contamination in a fluid sample such as water, involving the use of a filter material having a surface adapted to receive the sample in order to retain substantially all microbes from the sample on the filter surface under conditions that minimize the potential for contamination from sources other than the sample itself, and in a manner that permits the filter surface to be incubated in order to grow viable microbes contained thereon, in combination with a growth medium and an analytic instrument to permit analysis of the filter surface, within a predetermined incubation period, in order to determine whether the growth onset of viable microbes that may be present on the surface has begun.