The spectral line profiles of the doublet [Ca II] ~ 7291, 7323 and infrared triplet Ca iI %~ 8498, 8542, 8662 in the flux of the escaping radiation are calculated in the framework of spherically symmetric, isotropically expanding isothermal models of supernova shells~ Both the line profiles and the populations of the Ca + levels are calculated using the escape-probability method (Sobolev's approximation), modified to take into account the direct radiative coupling of the components of the Ca II muitipletso The calculated profiles of the multiplets are compared with those observed in the spectrum of SN 1987A at the times t = 198, 289, 399, 438 days, and this comparison is used to determine the physical parameters of the shell -- the electron temperature and the density distributions of the electrons and Ca + ions. i. Introduction Different Ca II lines are observed at different stages in the evolution of the spectra of type II supernovas. In the first days after the outburst, the spectra contain the infrared triplet Ca II (~% 8498, 8542, 8662) and the ultraviolet doublet of the H and K lines of Ca II (%% 3934, 3968)~ At a later stage, the doublet of forbidden lines (%% 7291, 7323) appears in the spectrum. The presence in the spectrum of both allowed and forbidden Ca II lines makes it possible, using the intensity ratio of these lines, to determine parameters of the supernova shell such as the electron temperature and electron density. The shape of the Ca II line profiles (especially of the infrared triplet) also depends on the density distribution in the shell. It should also be noted that in general the calculations of the profiles of the infrared triplet must take into account the direct radiative coupling between the components of the triplet; this can be effective because of the Doppler shift of the photon frequencies in the expanding shell. For supernovas, this coupling has not been taken into account in detail, and the profiles of the Ca II infrared triplet have been calculated in the classical (local) Sobolev approximation [i]