Data obtained from a pair-mated ostrich flock located at Oudtshoorn in South Africa were used to derive line differences for live weight and reproduction performance in sexually mature ostriches of the Zimbabwean Blue (ZB) and South African Black (SAB) strains during 2003 to 2006. At the commencement of breeding ZB breeding stock were, on average, between 9 and 13% heavier than SAB contemporaries. At the cessation of breeding the superiority of ZB birds was reduced to between 4 and 8%, expressed relative to SAB breeding stock. Live weight at the commencement of breeding was complicated by an interaction between sire line and year. The interaction resulted from no line differences between SAB and ZB males in 2003, contrasted to marked differences in subsequent years. Egg production was affected by dam line, but not by the line of the sire or the interaction between dam line and sire line. Egg production of SAB females was almost twice that of ZB contemporaries, at respectively 43.3 and 23.3 eggs per season. The number of infertile eggs was not affected by any of the independent variables considered. The number of shell deaths was affected by both sire line and dam line. Overall, SAB females sustained lower levels of shell deaths than ZB females, while the eggs produced by mates of SAB males had higher shell deaths than mates of ZB males. Chick production was affected by dam line; the effects of sire line and the dam line x sire line interaction being non significant. Overall, SAB females produced more than double the number of chicks produced by their ZB contemporaries, at respectively 23.1 and 10.6 chicks per season. Both egg production and chick production were affected by a dam line x year interaction. No dam line difference was observed during 2003, whereas SAB females clearly outperformed ZB females in subsequent years. Further studies on the ostrich bloodlines and their crosses are needed to devise a selection and crossbreeding strategy for improving production and profitability in the industry.