The effects of year, sex of lamb, breed of dam, and breed of sire were estimated for age at puberty, breeding to lambing interval, breeding weight, ovulation rate, and ewe productivity (weight of lamb weaned per ewe exposed) and its component traits in F1 ewe lambs produced from Suffolk and Targhee ewes mated to rams of three wool breeds (Finnsheep, Combo-6, and Booroole Merino) and two hair breeds (St. Croix and Barbados). Ewe lambs were pasture-mated to Dorset rams when they were 8 to 10 mo of age. A total of 334 F1 ewe lambs, born in the late winters of 1986 through 1989, were exposed Year of birth was an important source of variation for age at puberty (P < .05), breding weight (P < .01), fertility (P < .05), prolificacy (P < .10), lamb survival (P < .10), lamb weaning weight (P < .05), and ewe productivity (P < .01). Ram lambs born to the F1 ewe lambs had lower (P < .10) survival rates to weaning but were heavier (P < .01) at weaning than contemporary ewe lambs. The F1 ewe lambs from Suffolk dams reached puberty earlier (P < .01), were heavier (P < .01) at breeding, and had higher (P < .01) ovulation rates and greater (P < .01) prolificacy than ewe lambs from Targhee dams.(ABSTRACT TRUNCATED AT 250 WORDS)