This paper reviews the literature regarding variations of the kanban system, i.e. the aim is to study only the modified kanban systems. Thirty two different systems were studied and classified according to six categories: the publication year of the paper, the number of original characteristics conserved in the variation, the operational differences between each variation and the original kanban system, the advantages in relation to the original kanban, the disadvantages in relation to the original kanban, and the way those systems were tested. A brief summary of each adaptation is shown, integrating the scattered efforts undertaken by the authors with the aim of improving the kanban system and adjusting it to the new and/or distinct necessities of the production systems. Our analysis of the papers, using the proposed classification method, provides useful insights on the anatomy of the literature about variations of the kanban system. It was found that, among other topics, there is a great difference between the quantity of theoretical and practical proposals.