A polysulphide resin composition is cured by reacting a liquid polysulphide resin with an isocyanate curing agent in the presence of an organometallic or metal salt catalyst, preferably an organotin catalyst such as dibutyltin laurate (DBTL). The compositions have utility in thin films and coatings, and in the bonding, sealing and coating of polycarbonates. Aliphatic isocyanates are preferred for applications where clear coatings are required, the more reactive aromatic isocyanates being preferred for other applications.