A quadratic isoparametric "nite element formulation based on the "rst order shear deformation theory is presented for the free vibration and transient response analysis of multiple delaminated doubly curved composite shells subjected to a hygrothermal environment. A simple multiple delamination model developed by the authors earlier is employed to take care of any number/size of delamination located anywhere in the laminate. The analysis takes into account the lamina material properties at elevated moisture concentration and temperature. Newmark's direct integration scheme is used to solve the dynamic equation of equilibrium at every timestep during the transient analysis. Several numerical examples are considered and the results are compared with those available in the literature. The results show a reduction in the fundamental frequency with an increase in the percentage of uniform moisture content as well as temperature for simply supported antisymmetric crossply and angleply laminates for any size of delamination considered. The central dynamic displacements and the stresses at the center of laminates are observed to increase due to the e!ect of moisture/temperature subjected to the suddenly applied uniform pulse loading 2001 Academic Press