The effect of homogenization on the heat stability characteristics of milk was examined. The heat stability of homogenized milk, as determined by the time taken for protein clots to form when heated at 140 °C, was reduced with increasing pressure in the range 3·5–34·5 MPa. The heat stability of homogenized milks was greater for samples obtained in the summer months than for those obtained in the winter. The general destabilizing effect of homogenization could be partly offset by 2-stage homogenization (20·7 MPa followed by 3·5 MPa), addition of phosphate stabilizers (0·08% w/v) or homogenization at a high temperature (65 °C). Whilst homogenized and unhomogenized milks reacted similarly to the addition of Ca, phosphate stabilizers, sulphydryl-blocking and oxidizing agents, the effects of season, addition of urea or formaldehyde were different for homogenized milk.