Synthetic sulfide ore deposits constructed and tested in our laboratory confirm that oxidizing sulfide deposits generate detectable amounts of COS and CS2. Most of the COS in these experiments was adsorbed onto the soil overlying the sulfide material, indicating that surveys designed to measure COS variations should make use of gases desorbed from soil. In contrast, most of the CS2 in the experiments was found in the head space air, indicating tht it would be most easily detected in surveys collecting and analyzing interstitial soil gas. The lack of CS2 adsorbed onto soil is probably a result of its oxidation to COS after being adsorbed onto soil during our experiments.