Mast cells are known to be present in normal liver tissue but the data on their association with diseases of the liver are limited. In this study we used a long toluidine blue technique to investigate the mast cell numbers in 20 normal and 45 diseased liver biopsies containing granulomas (20 tuberculosis, 14 sarcoidosis, 4 schistosomiasis, 4 neoplasia-associated, 3 drug idiosyncrasy). Our results show that the mast cells are regular constituents of normal portal tracts and the amount of mast cells in the diseased samples corresponds to the area occupied by non-parenchymal tissues. As compared to normal controls, significantly less mast cells were present in biopsies from tuberculosis patients (p less than 0.025). Highest numbers were found in the schistosomiasis group. No link between the mast cell numbers and the cause of the granulomas could be demonstrated.