Algae have been commonly used to establish time of death in drowning victims and to link suspects to crime scenes. Recently, the potential use of algae and other aquatic organisms in the estimation of PMSI has received increased attention. However, algal community composition has been examined as a qualitative approach to the estimation of PMSI; no quantitative studies have yet examined algal growth rates as PMSI indicators. The current study examined pig decomposition in streams in order to probe the quantitative use of algal as an indicator of PMSI. Both pigs and ceramic tiles were completely submerged between November 2000 and April 2001 in two second-order streams in Pennsylvania and were regularly sampled for periphyton growth. Five stages of decomposition were noted for the pig carcasses. The algal growth rates were measured quantitatively as a function of chlorophyll-a concentration; algal growth rates were greater on the pig carcasses than on the tiles. The microhabitat was not observed to influence algal growth. A strong correlation was noted between algal growth rates and time on pigs and tile substrates, especially as observed following significant rain events. Thus, algal growth rates may be a useful quantitative indicator of how long a body has been submerged in streams or riverine habitats. Figures, tables, references