We report on the drug packaging, masking, and distribution procedures for a large double-masked, randomized, controlled, crossover trial. The Study of Inactivated Influenza Vaccine in Asthmatics was performed to evaluate whether influenza vaccination was safe for asthmatics. Nineteen clinical centers enrolled 2032 participants from 15 September to 30 November 2000. The participants were assigned individual kits with two syringes (placebo and vaccine); the order of injection was randomly assigned. All participants enrolled in the trial received the first injection and 2009 participants received the second injection. Five participants received their injections in the wrong order; we have no evidence that any participant received an injection from the wrong kit. Challenges faced by the trial were a manufacturing shortage of vaccine, the lack of a commercially available placebo, short time periods for planning and startup, and a diverse set of clinical centers. Utilizing individual syringe kits, using the same identification for patient, kit, and drug assignment, and dispensing drug from a central facility helped to successfully meet these challenges.