Amperometric trace determination of Os(VIII) was successfully carried out with the help of thioglycolic acid at dropping mercury electrode (DME) in 0.5M NaOH medium. The metal to ligand ratio was found to be 5:1. The method enabled the estimation of Os(VIII) solution up to 3.80ppm with maximum error (±2%) in the case of most dilute solutions only. The interference of various ions has also been investigated. The method is found to be fairly selective, sensitive, rapid, precise, accurate and economic.