Many patients find it difficult to swallow tablets and hard gelatin capsules and do not take their medication as prescribed. It is estimated that 50% of the population is affected by this problem which results in a high incidence of non-compliance and ineffective therapy. The difficulty is experienced in particular by paediatric and geriatric patients, but it also applies to people who are ill in bed and to those active working patients who are busy or travelling, especially those who have no access to water. Such problems can be resolved by means of the Zydis dosage form which does not require water to aid swallowing. The Zydis fast-dissolving dosage form is a unique freeze dried medicinal tablet, made from well known and acceptable materials. When Zydis units are put into the mouth, the freeze dried structure disintegrates instantaneously releasing the drug which dissolves or disperses in the saliva. The saliva containing the dissolved or dispersed medicament is then swallowed and the drug is absorbed in the normal way. Some drugs are absorbed from the mouth, pharynx and oesophagus as the saliva passes down into the stomach. In these cases, the bioavailabilities of drugs from Zydis formulations are significantly greater than those observed from standard dosage forms. This paper deals with the formulation and process technology of the Zydis dosage form. The bioavailability characteristics of Zydis products are summarized, and in particular, the design of Zydis products for the enhancement of oral bioavailability and the improvement of clinical activity, through transmucosal delivery and pregastric absorption, is discussed.