In recent years, an increasingly high proportion of the country's ewes have been housed indoors for lambing, penned at high population densities. When observing suckling, for other purposes (Horrell et al. , 1987), we noticed that there seemed to be frequent disturbances of the normal suckling routine. The general pattern of suckling in extensive conditions has been described (Ewbank 1967). It involves suckling at fairly regularly intervals, with uninterrupted sucking for a period of 1-5 mins (in the first week) declining to 10-25 seconds in older lambs, until either the ewe moves away or the lamb ceases spontaneously; lambs rarely attempt to suck at unrelated ewes and twins tend to suck together. In contrast, we saw many attempts by lambs in indoor pens to suck at unrelated ewes, and ongoing suckling often seemed to be disturbed early on by alien lambs intruding, aggression on lambs by the ewe, lambs knocked off by other ewes, and other external events. If these differences are considerable, Intensive lambing conditions may have important implications for the efficiency of milk interchange. This project was designed to compare systematically the pattern of suckling in extensive and intensive conditions and to quantify the Incidence of various disturbances of suckling.