Theoretical and technical aspects of breeding hybrid rice cultivars are considered in this manual under the headings: (1) heterosis in rice; (2) rice cytoplasmic-genetic male sterility system; (3) procedures for breeding hybrid rice; (4) breeding for CMS lines and their maintainers; (5) breeding for restorer lines; (6) hybrid seed production and CMS line multiplication; (7) purifying parental lines and producing foundation seeds; (8) hybrid rice cultivation practices; (9) breeding two-line system hybrid rice; and (10) studies on one-line system hybrid rice development.