The aim of this study was examine the rehydration, swelling and drug release behavior of spherical pellets containing theophylline and coated with two different calcium pectinates. The spherical pellets were prepared by an extrusion-spheronization method and then coated with calcium pectinate using the diffusion-controlled interfacial complexation technique, which provides a defect-free and uniform coating on solid cores. The effect of pellet size, pectin type, pectin concentration and dissolution medium on the swelling and drug release behavior was investigated by a multi-level factorial design approach. Theophylline release from the pellets was slowed by the application of the coatings. The time to release 50% of the payload (ie T50) in an acidic medium was 7 minutes from uncoated small pellets and was 55 minutes after an amidated calcium pectinate coat was applied; a comparable coat on large pellets showed a T50 of 93 minutes. Drug release profiles of dry coated pellets showed a lag time (all less than 20 minutes) when the gel coat hydrated and swelled, followed by a zero-order release. It was found that the release rate was controlled by the pellet size, pectin type, pectin concentration and dissolution medium.