We have successfully prepared "self-bursting" microcapsule. The microcapsule retains its shape when suspended in water but breaks open quickly after the water evaporates. In this report, the breaking behavior of MC, which encapsulated insecticide (pyriproxyfen) with polyurethane via an interfacial polymerization method, was studied. In order to investigate the self-bursting phenomenon more detail, we studied the relationships between the self-burst ratio and the self-weight of the microcapsule, capillary force, and critical buckling stress. As a result, it was found that wall thickness affected the self-bursting phenomenon. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.