These experiments were performed in Agronomy Department, Faculty of Agriculture, Al-Azhar University, during 2008/2009 and 2009/2010 seasons to investigate the allelopathic potential effect of five weed species viz. Chenopodium album, L. (W₁), Euphorbia peplus, L. (W₂), Melilotus indica, (L.) All. (W₃),  Avena fatua, L. (W₄) and Phalaris minor, Retz. (W₅) on germination and seedling development of wheat (Triticum aestivum, L. local var. Sakha 94). So,two experiments were carried out, the first (in laboratory) to study the effect of weed parts (root and shoot) water extract at different concentration (0,10, 20 and 30%). The second experiment (in wirehouse) to study the effect of previous weed shoot residues at different concentration (0,1, 2 and 3% (w/w)). Results of the first experiment indicated that the differences between weed species for all studied traits were significant in the means of two seasons. All extracted of Chenopodium album, L. and Melilotus indica, (L.) All. significantly inhibited germination %, germination rate, root length, shoot length, root and shoot dry weights compared with other weed species. The differences between weed parts extracted were significant for all studied traits in the means of two seasons. Shoot extraction significantly inhibited all studied traits. Also, results indicated that the differences between extract concentrations were significant for all studied attributed in the means of the two seasons. Application 30% concentration significantly decreased grain germination and seedling growth of wheat. All the interactions between weed species, weed parts and concentration extracted were significant, except germination rate in the means of two seasons. Melilotus indica, (L.) All. × the shoot extract × 30% concentration increased effective allelopathic on all studied attributes under experiment conditions. Results of the second experiment indicated that the effects of weed residues species and concentrations on seedling growth of wheat were significant in means of two seasons. The interactions between different species and 3% concentration were significant for all studied traits. Avena fatua, L.and 3% concentration significantly inhibited most studied traits in means of two seasons.