Research indicates that myeloablative hematopoietic cell transplantation (HCT) impairs neurocognitive function. However, prospective studies on long-term effects are lacking. This longitudinal study examined neurocognitive changes over the first year in 142 adult recipients of allogeneic HC transplants who received neuropsychologic testing before transplantation and again after 80 days and 1 year. Age-, sex-, and education-adjusted population-based standardized scores were used for normative comparisons. Performance on all tests declined from before transplantation to 80 days (P < .05) and improved by 1 year (P < .05), returning to pretransplantation levels on all tests except for grip strength and motor dexterity. Although verbal fluency and memory recovered by 1 year, both were below norms at all 3 testing times (P < .01). Logistic regressions indicated that patients without chemotherapy, other than hydroxyurea, previous to HCT and patients not receiving chronic graft-versus-host disease (GVHD) medication at 1 year had lower risk of impaired function (P < .05). In conclusion, HCT was associated with significant generalized decline in neurocognitive performance at 80 days, with subsequent recovery to pretransplantation levels by 1 year for most survivors, except on motor tasks. Results indicate that long-term cognitive decrements, as distinct from motor disabilities, infrequently derive directly from HCT.