The concept of mark of a permutation group was introduced by Burnside in 1911. Redfield rediscovered marks in 1930s but his work was not published until 1984. He used marks to count group reduced distributions according to their symmetry groups. Marks have been used by several other authors; Sheehan [10] used marks to count the number of graphs with a given automorphism group, Lloyd [7] counted isomers using marks, Kamuti [4] used marks to find subdegrees of primitive permutation representations of PGL (2, q), Kimani et. al. [5] used marks to compute the ranks and subdegrees of the symmetric group acting on ordered pairs and ordered triples while Rimberia and Kamuti [9] used marks to find the subdegrees of primitive permutation representations of the symmetric group In this paper, we enumerate the number of stereoisomers derived from trigonal bipyramidal molecules using the mark version of Redfield superposition theorem. Results show that Iodotricarbonyl (triphenylphoshine) – cobalt (1) complex has 4 stereoisomers while a trigonal bipyramidal complex of the type MABCDE has 20 stereoisomers.