A number of practical advantages have made the nematode Caenorhabditis elegans a useful model for genetic and developmental biological research. These same advantages, along with conservation of disease and stress response pathways, availability of mutant and transgenic strains, and wealth of biological information, have led to the increased use of C. elegans in toxicological studies. Although the potential to study the mechanisms of developmental toxicology in C. elegans is promising, embryonic and larval growth tests to identify compounds that affect the nematode have remained the primary use of C. elegans in developmental toxicology. Here, we describe a C. elegans larval growth and development assay for medium- and high-throughput screening using the COPAS Biosort flow cytometer and provide descriptions of the data and subsequent analysis.