The chemical coding scheme of the Medical Coding Scheme (MCS), developed for use in the Comparative Systems Laboratory (CSL), is outlined and evaluated in this report. The chemical coding scheme provides a classification scheme and encoding method for drugs and chemical terms. Using the scheme complicated chemical structures may be expressed concisely by a single line of letters and numbers. The scheme was developed so that it could be used independently or as a part of a larger coding scheme. One of the objectives of the chemical coding scheme was to investigate the performance and problems related to the handling of chemical information in the field of biomedicine by computer. The chemical coding scheme is a way of coding chemical compounds for mechanical retrieval and, to a degree, bypasses the present confusion existing in chemical nomenclature. Despite limitations and faults in the coding scheme, a relatively high degree of inter-and intra-coder consistency was achieved. (Author/CC)