Blair and McPherson's implicit definition of alluvial fans will undoubtedly create problems for earth scientists, especially geomorphologists, because it is too restrictive to encompass the wide diversity of natural depositional conditions. What we propose to do is use the Okavango 'fan', which represents an extremely unusual depositional setting, and which Blair and McPherson classify as a 'mud-dominated river delta', as a test case of fan classification in order to illustrate the shortcomings of their classification scheme.