<p>This population-based retrospective cohort study sought to determine if anorexia nervosa (AN) is associated with a higher risk of urolithiasis. Nine thousand three hundred two females with AN were compared to 92 959 randomly selected age-matched and practice-matched females. Cox regression was used to estimate the hazard ratio (HR) for urolithiasis and evaluate effect modification by age. Twenty-three participants with AN (0.25%) developed urolithiasis compared with 154 unexposed participants (0.17%) over a median of 4&nbsp;years of observation. The risk of urolithiasis varied significantly with age (interaction p = 0.02). AN was associated with a more than threefold higher risk of urolithiasis in females ≤25&nbsp;years of age (HR 3.49, 95% CI: 1.56-7.81; p = 0.002), but not in females over 25&nbsp;years (HR 1.18, 95% CI: 0.69-2.02; p = 0.54). The distribution of diagnosis codes for urolithiasis differed between groups (p = 0.04), with a higher proportion of codes for uric acid urolithiasis in the AN (16.2%) versus unexposed group (5.0%). Copyright © 2017 John Wiley &amp; Sons, Ltd and Eating Disorders Association.</p>