SummaryAn accidental chlorine gas leakage in a chemical plant in the vicinity of Ghent permitted us to observe the effects on 14 patients within the first 30 hours, and to perform pulmonary function tests.We obtained a 3 month follow-up. We were particularly interested in the acute and subacute changes after the exposure.The accident was provoked by the uncoupling of a chlorine gas pipe situated on an inner court. A yellow-green cloud formed in which the workers stayed between 3 and 30 minutes.Twenty-two workers were involved in the accident, but only fourteen could be fully observed.They were admitted to the emergency room within the first eight hours after the accident.On admission they received oxygen (51/min.) with an oxygen mask during 3 to 6 hours. One heavily exposed worker received antibiotics and stayed for one week in the hospital; the others could leave the hospital after the first pulmonary function tests.