The present study was intended to develop a new oral mucosal dosage form with a view to solving the problems of the administration of insulin by injections. We prepared a potentially suitable dosage form and tested it in beagle dogs. The new oral mucosal dosage form of insulin consists of the core-base, which contains cacao butter, insulin and additive, and the peripheral-base, which contains a mixture of hydroxypropyl cellulose-H (HPC) and Carbopol-934 (CP). The suitable mixing ratio of HPC and CP in the peripheral-base was chosen as 1 : 2 on the basis of experimental results concerning the stickiness, dissolution properties, viscosity and fracture resistance. This dosage form could stick tightly to the oral mucosa of beagle dogs for 6 hr. The change of blood sugar and plasma insulin levels in beagle dogs was investigated by the three-way crossover method with group A as a reference, group B given insulin alone and group C given insulin and sodium glycocholate. Absorption of insulin was recognized only in group C, indicating that sodium glycocholate effectively promoted the absorption of insulin from the oral mucosa. The percentage absorbed of insulin in this dosage form was about 0.5% compared with the amount absorbed upon intramuscular injection of insulin.