Two parallel schemes of crosses were practiced during five years involving the Spanish maternal line called V-line (V) and Saudi Gabali (S) rabbits. The first scheme began by crossing Saudi Gabali bucks and V line does to get the F1 (½S½V), then does and bucks of this F1 were inter-se mated to get the F2 (½S½V)2 and at the same time does of F1 were backcrossed with bucks of V line to get ¾V¼S, then progeny of the backcross were inter-se mated to get (¾V¼S)2, followed by four generations of inter se mating of (¾V¼S)2 to get a new synthetic maternal line named Saudi 2. The second scheme began by crossing V-line bucks with Saudi does to get the F1 cross (½V½S), then does and bucks of this F1 were inter-se mated to get the F2 (½V½S)2 and at the same time does of F1 cross were backcrossed with Saudi bucks to get ¾S¼V, then progeny of this backcross were inter-se mated to get (¾S¼V)2, followed by four generations of inter se mating of (¾S¼V)2 to form a new synthetic paternal line named Saudi 3. A total of 3496 litters of 922 does fathered by 199 sires and mothered by 451 dams were evaluated for litter size at birth (LSB) and weaning (LSW), litter weight at birth (LWB) and weaning (LWW) and pre-weaning litter mortality (PLM). A generalized least square procedure was used to estimate additive and heterotic effects (direct, maternal, and grand-maternal), direct recombination effect and cyto-plasmatic effects. Across the six generations studied, superiority rates for does of the two synthetic lines developed were 15.7, 18.2, 5.9, 16.9, and -9.2 in LSB, LSW, LWB, LWW, and PLM comparable to purebreds does, respectively. Crossbred does, dams and grand-dams showed moderate estimates of direct, maternal, and grand-maternal heterosis for litter traits studied.