An investigation has been undertaken to assess, in vitro, the potential of several pectin formulations as colonie drug delivery systems. Experiments were conducted on the release of model compounds from matrix tablets under conditions pertaining to those in vivo. The monitoring of release gives a sensitive indication of the behaviour of the pectin under the different conditions. The type of pectin, the presence of calcium and the solubility of the calcium salt all influence release. Additionally, pectins with a low degree of methoxylation were more susceptible to enzymic breakdown. Calcium enhanced the enzymic activity. Rheological studies indicated that gel strength was a factor in determining release. These findings suggest that either a high methoxy pectin formulation or a low methoxy pectin with a carefully controlled amount of calcium should maximise colonie specificity by providing optimal protection of a drug during its transit to the colon and a high susceptibility to enzymic attack.