Diphenyl disulphide has been shown to generate hydrogen peroxide in erythrocytes in vitro. It also induces oxidative damage (reversible and irreversible haemoglobin oxidation, depletion of non-protein and protein-bound thiols) in these cells. Such changes were also recorded in erythrocytes exposed to 4,4'-diaminodiphenyl disulphide, 2,2'-diaminodiphenyl disulphide, 4,4'-dimethyldiphenyl disulphide, 4,4'-dinitrodiphenyl disulphide, diphenyl disulphide-2,2'-dicarboxylic acid and dibenzyl disulphide. The relative potency of these compounds in causing erythrocyte damage is correlated with their ability to generate 'active oxygen' species in vitro.