The cellular content of myeloperoxidase (MPO), chymotrypsin-like cationic protein (CCP) and lactoferrin (LF) of isolated polymorphonuclear leucocytes (PMNs) from pregnant women were analysed by immuno-chemical methods. The cellular levels of MPO and CCP were unaltered during pregnancy while the cellular levels of LF were increased during pregnancy and post partum (P less than 0.01). Peroxidase activity within isolated PMN was analysed by two methods, a Guaiacol method and a Chemiluminescence method. The activity was found to be reduced during pregnancy. The reduction was explained by the reduction in eosinophil peroxidase which in turn was a consequence of a reduced number of circulating eosinophils during pregnancy.