Objective: Delayed-release mesalamine 400 mg capsules containing four 100 mg tablets have been developed for children with ulcerative colitis who have difficulty swallowing. Bioavailability of the mesalamine capsules was compared with existing mesalamine tablets in healthy adults, and the effect of food on bioavailability from mesalamine capsules was determined. Tablet swallowability in healthy children was evaluated. Methods: In the open-label, replicate-treatment, single-dose, crossover, comparative bioavailability study, healthy adult volunteers were randomized to one of four treatment sequences to receive mesalamine 400 mg tablets (fasted) twice, mesalamine 400 mg capsules (fasted) twice, and a mesalamine 400 mg capsule (with food) once, with ≥7 days between treatments. Pharmacokinetic (PK) parameters were calculated and analyzed using the reference-scaled average bioequivalence procedure. In the open-label, single-dose swallowability study, healthy children aged 5–11 years were asked to swallow eight placebo tablets identical to those contained in two mesalamine capsules. Results: In the bioavailability study (n=160), mesalamine capsules and tablets in fasted volunteers exhibited similarly delayed absorption and were shown to be bioequivalent; statistical parameters calculated from PK values met the criteria for bioequivalence. A slight increase in mesalamine bioavailability was observed with food administration, but the delayed-release performance of the capsules was not affected. Overall safety profiles between capsules and tablets were similar. In the swallowability study (n=60), the majority of children swallowed eight placebo tablets, with slight variability between age groups. Conclusion: Evaluation of PK parameters confirmed mesalamine capsules are bioequivalent to mesalamine tablets. Mesalamine capsules were well tolerated, can be administered with or without food, and are an age-appropriate product for children.