Authors in 1968 performing the periodoc observation of persons, working in toluene-containing athmosphera noticed the presence of hepatomegaly. Laboratory tests performed in 1968--1976 have revealed increase of the level of GOT. At 22 workers out of 170 liver biopsy was performed. By electron microscopy pathologic alterations in the mitochondria and in the rough-surfaced endoplasmic reticulum could be observed, -since these organella contain the two-third of the GOT of hepatocytes. It is assumed that mitochondria as sources of energy take part in the process of the oxydation of toulene, ribosomes of the rough-surfaced endoplasmic reticulum in the conjugation of benzoic-acid with glycine. Authors assume that there is a correlation between the damage of the organella and the detoxication of the toluene by hepatocytes.