Line x tester experiment was conducted to evaluate the performance of 25 F1 hybrids along with ten parents in rice at Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt during 2007 and 2008 growing seasons to estimate the percentage of heterosis and heterobeltiosis among F1 hybrids developed from five lines and five testers of rice. Genotypic mean squares for all studied traits were highly significant and had genetic variability for these traits. Heterosis and heterobeltiosis were estimated for number of days to maturing, plant height (cm), number of panicles per plant, panicle weight (g), 1000-grain weight (g), and grain yield per plant in cross combinations of five lines of rice (Giza 177, Sakha 101, Sakha 103, Sakha 104 and one promising line GZ6903-1-2-2-1) and five testers (IRBLI-F5, IRBLzFU, IRBLz5-CA, IRBLTACT2 and IRBLSH-B). The resultes exhibited significant differences among genotypes and their crosses for all studied traits. The crosses Sakha 101 x IRBLzFU and Giza 177 x IRBLzFU depicted significant heterosis and heterobeltiosis for grain yield and most of the other studied traits followed by Giza 177 x IRBLI-F5. Heritability estimates in broad sense were high for all studied traits. While, heritability estimates in narrow sense were relatively low for all traits.