Different commercially available CP-Sil 8 CB capillary columns have been tested with a mixed standard containing methyl mercury chloride, ethyl mercury chloride and a stable nonpolar chlorinated hydrocarbon. The aim of the study was to see whether the columns tested could be used without special pretreatments and precautions for the determination of organo-mercury compounds. The GC conditions in these determinations where similar to those conditions used for the determination of chlorinated pesticides. The best peak shapes where found using a normal packed column injector, modified with a commercially available insert for on-column injections on wide bore columns, and a 5.35 mum thick stationary phase. It was concluded that this CP Sil 8 CB column gave good results although minor interactions between the organo-mercury compounds and the column could be seen.