Practical and accurate microbial assessment of environmental systems is predicated on the detection and quantification of various microbial parameters in complex matrices. Traditional growth-based assays, considered to be both slow and biased, are increasingly being replaced by optical detection methods such as flow cytometry. Flow cytometry (FCM) offers high-speed multi-parametric data acquisition, compatibility with current molecular-based microbial detection technologies, and is a proven technology platform. The unique technical properties of flow cytometry have allowed the discrimination of bacteria based on nucleic acid staining, microbial identification based on genomic and immunologic characteristics, and determination of cell viability. For this technology to achieve the ultimate goal of monitoring the microbial ecology of distributed systems, it will be necessary to develop a fully functional, low cost, and networkable microsystem platform capable of rapid detection of multiple species of microorganisms simultaneously under realistic environmental conditions. One such microsystem, miniaturized and integrated in accordance with recent advances in micro-electro-mechanical systems technology, is named the Micro Integrated Flow Cytometer. This manuscript is a minireview of the current status and future prospects for environmental application of flow cytometry in general, and micro-flow cytometry in particular.