Noncollinear second-harmonic-generation (SHG) processes involving an unfocused laser ham and itS scattered radiation produce one or more cones of phasematched second harmonic. On the principal xoz plane, the expressions of the ring parameters in terms of .the indices of refraction and geometry in biaxial crystals are derived. The numeric solutions are in good agreement with observed rings. A method for determining the optimum direction in SHG is suggested.