The encapsulation of micro-organisms such as bacteria and fungi in biopolymers is currently being evaluated as delivery systems in many fields. Information about the viability and morphology of the organisms in the microparticle is often required to ascertain the longevity of the systems. A rapid method using fluorescent stains for microbial viability has been validated for organisms within alginate microparticles. Usually viability is assessed by dissolving the microparticles and cell culturing. This new method is advantageous for slow growing or filamentous organisms because these are not quickly or accurately enumerated by plate counts. In addition, the technique also allows the morphology of the organism to be monitored over time.