  Skewness of temperature fluctuations of the cosmic microwave background (CMB)
produced by initially Gaussian adiabatic perturbations with the flat
(Harrison-Zeldovich) spectrum, which arises due to non-linear corrections to a
gravitational potential at the matter-dominated stage, is calculated
quantitatively. For the standard CDM model, the effect appears to be smaller
than expected previously and lies below the cosmic variance limit even for
small angles. The sign of the skewness is opposite to that of the skewness of
density perturbations.
