The wild species of Oryza are an important reservoir of desirable genes for resistance to major diseases and insect pests, tolerance to several abiotic stresses and also a good source of cytoplasmic male sterility.Even though resistance sources are available in cultivated rice germplasm, the resistant varieties are becoming susceptible to pest and diseases due to change in insect biotypes and pathogen races. In order to create genetic variability and broaden the gene pool of rice there is a need to look for useful genes from alien germplasm sources.Thus there is an urgent need to broaden the rice gene pool by introgression of alien genes from wild rice species to meet the challenges affecting rice production. Wide hybridization in rice is a cross between wild rice species and the cultivated variety. This is normally difficult to achieve because many wild species of the genus Oryza fail to hybridize with cultivated rice due to differences in chromosome number or genetic constitution. Fertilization may occur but the embryo is aborted. This necessitates the use of embryo rescue and tissue culture techniques to get viable seeds.Details of alien gene introgression have been discussed in this review.