In order to investigate the influence of various environmental pollutants on living organisms, the effects of hlogenated hydrocarbons on the mitochondrial membrane were examined. The results obtained were as follows: 1) Monohalogenated benzenes decrease state 3 respiration and increase state 4 respiration, resulting in a decrease in both respiratory control (RCI) and the ADP/O ratio. 2) The above activity is in the decreasing order of iodobenzene, bromobenzene, chlorobenzene and fluorobenzene. This order of activity is parallel to that of potassium releasing activity. 3) Similarly to the effect of monohalogenated benzenes, brominated hydrocarbons also decrease both RCI and the ADP/O ratio. The activity is in the decreasing order of tribromobenzene, dibromobenzene, boron carbide, monobromobenzene and bromoform, which parallels the potassium releasing activity.