Objective: To compare outcomes for young adults conceived by assisted reproductive technology (ART) with non-ART-conceived young adults. Design: Cohort study. Setting: Not applicable. Participant(s): Mothers and their offspring (aged 18-28 years) conceived by ART; mothers and their non-ART-conceived offspring, randomly selected from the same source population. Intervention(s): Structured telephone interviews, one with mothers and another with their young adult offspring. Main Outcome Measure(s): Maternal report on young adult offspring hospitalizations and chronic illness accumulated over the first 18 years of their lives; young adult self-report on perceived current quality of life, body mass index, pubertal development, and educational achievement. Result(s): Of 1,480 eligible ART mothers, 80 were traced and contacted. Of those, 656 (55 ) participated, reporting on 705 ART-conceived offspring; 269 (23 ) declined participation and 262 (22 ) did not respond. Of the participants, 84 consented to contact with their young adult offspring, of whom 547 (92 ) participated. Random-digit dialing recruited 868 non-ART mothers and 549 offspring. Compared with non-ART young adults, the ART group had significant increases in three maternally reported outcomes: 1) hospital admissions, including those in the secondary school years; 2) atopic respiratory conditions; and 3) combined endocrine, nutritional, and metabolic disease ICD-10 category. Young adult reported outcomes were similar for both groups. Conclusion(s): This study addresses gaps in knowledge of outcomes beyond adolescence for those conceived by ART. Results show few adverse outcomes in this large cohort of young adults, but additional assessment through clinical review is required to address issues unable to be examined in this study.