For the prevention of the aggregation during microencapsulation, the effects and role of polyisobutylene(PIB), as a protective colloid, were studied. The effects of sealant treatment on the microencapsulation were studied. Methyldopa was microencapsulated with ethylcellulose (EC) by polymer deposition from cyclohexane by temperature change using PIB. The EC-microencapsulated methyldopa was sealed with spermaceti. The dissolution of methyldopa was influenced by the drug to wall ratio. When PIB was used, low aggregation of microcapsules occurred and the surface was smooth with a few pores. Treatment of microcapsules with spermaceti retarded the release of methyldopa, the release being affected by the percentage of sealant used and the particle size of the product.