The literature has recorded many models dealing with manpower forecasting and planning. The approaches used by the various authors are clearly disparate. This paper presents a taxonomy for manpower planning and forecasting methodologies and classifies the landmark developments in this field. The taxonomical schema is then applied to unify the models in consideration of the methods and the decision factors used for forecasting and/or planning. The taxonomy allows for the most complex model structure containing all the factors considered germane in the existing literature.