The aim of this study was to determine whether adjustment factors for lamb weight (covering ewe age, litter size, sex and lamb age) should be different for different types of flocks. The appropriateness of using common adjustment factors for all flocks was studied with respect to interaction between the adjusted effects and with region, flock size and production level. The survey was based on data from the Swedish Sheep Recording Scheme from the years 1981–83, comprising the main breed groups Swedish Peltsheep (P), Swedish Landrace (L), Swedish Crossbred (X), the imported heavy breeds (K) and some minor breeds Swedish Finewool (Lf), Swedish Rya (Lr) and Swedish Crossbreds with crossbred parents (X*X). Interactions with region revealed that ram lambs (P, L, X) and lambs born to one-year old ewes (P and X) were in general given slightly too high adjusted weights in the northern part of Sweden. K-Group ram lambs tended to be slightly favoured in the western region. The adjustment factors were appropriate in the average flock size, while lambs after one-year old ewes and ram lambs were in most cases given slightly too high adjusted weights in small flocks. In Peltsheep the adjusted weights for triplets were significantly too high in large flocks. Significant interaction effects were found predominantly between production level and ewe age and between production level and sex which resulted in too high adjusted weights for lambs after both one- and two-year old ewes and for ram lambs in flocks with high production level. Interaction effects in the Lf-, Lr- and X*X-breeds were seldom observed and did not deviate from their respective breed groups. The results of this study do not motivate special sets of adjustments which consider region, flock size and production level.