In this study, a series of polyurea microcapsules were prepared by interfacial polyconden-sation using various isocyanates as the oil soluble monomer and diethylenetriamine as the water soluble monomer. Nonionic surfactant, NP-10, was used as an emulsifier. The yields of microcapsules from aliphatic isocyanates were higher than those of microcapsules from aromatic isocyanates due to the flexibility of the aliphatic chains. Polyurea microcapsules obtained from aliphatic isocyanates were stable well above 25$0^{circ}C$ and showed better thermal stability compared to those obtained from aromatic analogs.