The aim of this study was to determine the sensitivity and specificity of the Kato-Katz technique in the absence of a gold standard using Bayesian modeling for the determination of S. mansoni and soil transmitted helminths infection (STHs) in Zimbabwe. The fomol ether concentration technique had a relatively higher sensitivity and increased the number of primary school children who needed treatment in the field compared to the recommended Kato- Katz technique alone.