Four hundred and twenty-one adult allogeneic haematopoietic stem cell transplant (HSCT) survivors participated in a cross-sectional study to assess sexual dysfunction and infertility post-transplant. Survey instruments included the Sydney Post-Blood and Marrow Transplant (BMT) Survey, Functional Assessment of Cancer Treatment (FACT) – BMT, the Depression, Anxiety, Stress Scales (DASS 21), the Chronic Graft-versus-Host Disease (cGVHD) Activity Assessment- Patient Self Report (Form B), the Lee cGVHD Symptom Scale and The Post-Traumatic Growth Inventory. Most HSCT survivors reported sexual difficulties (51% of males; 66% of females). Men reported erectile dysfunction (79%) and decreased libido (61·6%) and women reported loss of libido (83%), painful intercourse (73%) and less enjoyment of sex (68%). Women also commonly reported vaginal dryness (73%), vaginal narrowing (34%) and vaginal irritation (26%). Woman had much higher rates of genital cGvHD than men (22% vs. 5%). Age and cGVHD were significantly associated with sexual dysfunction. Few survivors had children following transplant (3·3%). However, for those of reproductive age at HSCT, 22% reported trying to conceive, with 10·3% reporting success. This study is the largest to date exploring sexual function in survivors of allo-HSCT. This data provides the basis for health service reform to better meet the needs of HSCT survivors, including evidence to support counselling and education both pre- and post-transplant. ; Funded by New South Wales Agency for Clinical Innovation Blood and Marrow Transplant Network