Although aviary systems for laying hens provide the freedom of movement advocated for good welfare, there are concerns for the general health and plumage conditions of birds kept in these larger social groups. In this study the authors addressed two management factors that may affect the incidence of problems in these systems, those of genetic strain and feed form. Hens of two different hybrid strains, both representing crosses of Rhode Island Red and Leghorn, were kept in groups of approximately 270 birds in aviary pens (3 x 5.8 m). Pens were fed either mash or pellet forms of the same diet. Thus, a 2 x 2 factorial of hybrid and feed type, with three replications per treatment combination was formed. Diet had little effect on plumage condition, general health or tonic immobility (measure of fear). The only significant effect of diet was on the occurrence of bumble foot (a condition of the feet), with it being more common when fed mash. The genetic hybrids differed in a number of traits including general health, cannibalism, salpingitis, and coccidiosis. However, each hybrid performed better in some of these traits than the other. The results suggest that genotype is an important consideration in managing hens in aviary systems.