Intraspecific hybridization among four cultivars of snapdragon, i.e. P₁ = Sonnet wit (white), P₂ = Sonnet karmijn (red), P₃ = Sonnet rose (rose) and P₄ = Sonnet geel (yellow) was carried out during three successive seasons: 95/1996, 96/1997 and 97/1998 at Antoniadis Botanical Garden, Horticulture Research Institute, Agriculture Research Center, Alexandria, Egypt. The main objective of this work was to produce new patterns of snapdragon, especially with reference to flower characteristics. Diallel cross analysis was used to study and determine the genetic system controlling flower traits and also the type of gene action for the different traits. The results showed that the additive and dominance gene effects were important in the inheritance of days to: first flower bud, showing colour and opening of the first floret. In the F₁, dominance gene effect was significant. The degree of dominance and Wr, Vr graph indicated overdominance in the F₁, but partial dominant in the F₂. Most of dominant genes acted toward earliness. The parents P₁ and P₂ have most dominant genes. All F₁ – progenies achieved negative heterosis towards the earliness. As for the number of spikes, the additive gene effects were important in the inheritance of that trait and overdominance was involved in the F₁ and F₂ generations. Dominance genes seemed to be acting in negative direction in the F₁, while in the F₂, dominance seemed to be acting in positive direction. Heritability in narrow sense was moderate in the F₁ hybrids but low in the F₂ generations, which indicated that environment effect had minor effect on this trait. Most of the F₁ – progenies obtained hybrid vigour. With respect to spike length, the additive and dominance gene effects were important in the inheritance of this trait and overdominance was involved. Dominance genes seemed to be acting in positive direction and increasing spike length. Narrow sense heritability was moderate in the F₁ but low in the F₂. Environmental component was significant in both generations. F₁ – progenies achieved hybrid vigour. As for the number of florets per spike, the dominance gene effect played the major role in the inheritance of this trait and overdominance was involved. In addition, additive gene variance was significant in the F₂ generations only indicating that it was possible to accumulate the favorable genes. Heritability in narrow sense was moderate to low in the F₁ hybrids and F₂ generations. Dominant genes seemed to be acting in positive direction and increased the number of florets. The two parents P₃ and P₄ seemed to carry most dominant genes. The F₁ – crosses obtained positive heterosis.