The operation of a set of computer programs for the reduction and qualitative analysis of mass spectral data from mixtures of organic compounds is described. The routines were developed for the analysis of data from fossil fuel materials but are applicable to any mixture of organic species. Data is processed by first sorting masses into homologous series and then placing the homologous series into groups which contain the same heteroatomic species. Within these groups series are ordered according to degree of unsaturation. Empirical formula possibilities are determined and plots of intensity versus mass are made for each homologous series. The routines are very general and can be used with any type of ionization process and with a wide variety of heteroatomic species. An example of the application of these routines to an aromatic nitrogen concentrate from shale oil is presented.