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An experiment was conducted over a three-year period to determine the effect of three management systems on performance and degree of parasitism of spring born market lambs. One hundred fifty-six Suffolk and Suffolk sired crossbred lambs (60, 48 and 48 in 1977, 1978 and 1979, respectively) were randomly alloted so as to balance the effect of sex, weight and breeding to one of three treatments: (1) pasture plus creep, (2) drylot and (3) an expanded metal floored pen. All lambs were fed a pelleted ration consisting of approximately 50% forage. Lambs were weaned at an average age of 60 days, wormed and isolated on a concrete floor for two weeks prior to the start of the test. Lambs were weighed at the start of the test and every four weeks for 84 days. Fecal samples were collected at the start of the test and at two-week intervals thereafter. Blood samples were collected at each weighing in 1978 and 1979. Fecal egg counts dictated when lambs were wormed. At the termination of the trials in 1978 and 1979, four lambs from each group were slaughtered and worms were recovered from the abomasa. Lambs fed in drylot gained significantly faster than either lambs fed on expanded metal or on pasture (.24, .21 and .17 kg/day, P < .05, for lambs on drylot, on expanded metal and on pasture, respectively). Lambs fed on the expanded metal floor gained significantly faster than those creep-fed on pasture (P < .05). Pastured lambs had consistently higher fecal egg counts per gram of feces and significantly higher worm counts at slaughter than did confined lambs (7.25, 2.81 and 0.98 epg, P < .05, for lambs on pasture, in drylot and on expanded metal, respectively). Worm numbers at slaughter were not significantly different for lambs fed in the two confinement groups. There was a highly significant negative correlation (r = .60, P < .01) between fecal egg count and packed cell volume.