Transsexuals vary in the sacrifices that they make while transitioning to their cross-gender group. We suggest that one influence on the sacrifices they make is identity fusion. When people fuse with a group, a visceral and irrevocable feeling of oneness with the group develops. The personal self (the sense of "I" and "me") remains potent and combines synergistically with the social self to motivate behavior. We hypothesized that transsexuals who felt fused with the cross-gender group would be especially willing to make sacrifices while transitioning to that group. Our sample included 22 male-to-female (MtF) and 16 female-to-male (FtM) transsexuals. Consistent with expectation, those who were fused with their cross-gender group (1) expressed more willingness to sacrifice close relationships in the process of changing sex than non-fused transsexuals and (2) actually underwent irreversible surgical change of their primary sexual characteristics (vaginoplasty for MtF transsexuals and hysterectomy for FtM transsexuals). These outcomes were not predicted by a measure of "group identification," which occurs when membership in the group eclipses the personal self (the "I" and "me" is subsumed by the group; in the extreme case, brainwashing occurs). These findings confirm and extend earlier evidence that identity fusion is uniquely effective in tapping a propensity to make substantial sacrifices for the group. We discuss identity fusion as a social psychological determinant of the choices of transsexuals.