Investigations utilizing a total number of 3998 farrowings from 1558 sows on two farms have shown a frequency of puerperal diseases (periparturient hypogalactia syndrome=PHS) of 32·7% and 27·0% respectively with significant differences between gilts and sows. Sows without PHS after farrowing (farm A) had a lower frequency of animals without oestrus after weaning of the piglets (0·3 V. 1·1%), a lower rate of late onset of oestrus (3·4% V. 5·9%, P<0·05), fewer sows had abortions (0·9 V. 2·3%, P<0·05) and a lower mortality rate (1·2 V. 4·1%, P<0·05) compared with sows which contracted puerperal diseases. The return rate was significantly lower in sows without PHS (12·4%, 16·1% in herds A and B) when compared with sows with puerperal diseases (15·8%, 21·7%, P<0·05). Also, the litter size of live born piglets was lower in sows with PHS when compared with healthy sows (farm A: 10·42 V. 10·66, P>0·05; farm B: 10·44 V. 10·80, P<0·05)