The study of ephemeral fever in cattle has defined a range of haematological and biochemical changes in blood which are characteristic of an inflammatory response. One of the clinical signs of ephemeral fever, a temporary paralysis reversible by treatment with calcium borogluconate, is similar to that in milk fever (parturient paresis), a disease of multiparous dairy cows. Three separate groups of cows were studied. Four multiparous cows were observed and sampled repeatedly during calving, three similar cows and one cow calving for the first time in a dairy herd were sampled daily before and after calving; and, in other dairy herds, seven cows with milk fever were sampled during illness. One of the cows under repeated observation during calving developed milk fever. The results showed that all the inflammatory indicators in blood were present in the multiparous cows at calving and that these were essentially similar to those established in ephemeral fever. The similarities in the four cows sampled repeatedly during the periparturient period were: a rectal temperature rise of 1 to 1.2 degrees C; rise in circulating neutrophils to peaks between 5700 and 11200 l-6; disappearance of eosinophils for 1 day; hypocalcaemia (plasma Ca < 2.0 mM l-1); fall of plasma zinc to low levels immediately after calving (plasma Zn < 500 micrograms l-1); fall of inorganic phosphate (plasma P < 0.9 mM l-1); rises in copper (plasma Cu > 1000 micrograms l-1) and plasma fibrin to > 8.75 g l-1. Plasma glucose peaked at calving between 5.7 and 8.9 mM l-1 then fell to levels ranging between 3.4 and 3.8 mM l-1. Plasma iron rose in one cow to 1220 micrograms l-1, was unchanged in one cow and fell in the other two to 440 and 860 micrograms l-1 respectively. The three multiparous cows which were sampled daily and calved normally showed similar haematological, macro and micromineral changes and fibrin response as did the seven milk fever cases. In the periparturient period, milk fever cows differed from multiparous cows calving normally, in degree but not in kind, of inflammatory response. It is postulated that an inflammatory event occurs in the periparturient period of multiparous cows which partially accounts for the falls in plasma calcium. This can precipitate a paralysis and other hypocalcaemic signs similar to that seen in acute ephemeral fever.