Previous work has shown that crystallization is suppressed in some thermotropic copolyesters containing between five and seven different units of different types (rod-like, crankshaft and rigid angular). However, no general rules for design of such copolymers could be formulated. It is now found that crystallizability of random copolyesters is related to probabilities of tetrads forming crystallizable sequences. Relationships for calculating the probabilities of such tetrads in random multicomponent copolyesters are derived. A criterion for design of non-crystalline copolyesters is formulated.