PURPOSE: To obtain a new adhesive/sealant compsn. contg. a single photoinitiator being effective to a slow cure component, a fast cure component and both of them and being useful for sealing cracks, rents and leak points.

CONSTITUTION: The objective compsn. comprises a slow cure component (A) consisting of a cation-polymerizable polyepoxide monomer, etc., a fast cure component (B) consisting of a free radicalpolymerizable acrylic monomer or substd. acrylic monomer, etc., and a single photoinitiator (C) consisting of an onium salt compd. or a metallocene, etc., in which the components A and B are polymerizable by different reactions which respectively proceed by two different speeds and the component C can initiate both polymn. of the components A and B when it is exposed to a radiation source.