The broad objective of this study was to isolate and identify the microorganisms causing mouldiness of stored yam chips and to look for ways of preventing the problem. Microorganisms isolated included Aspergillus flavus, A. glaucus, A. nidulans, A. niger, A. ochraceous, A. tamarii, A. candidus, Penicillium oxalicum, Trichoderma longibrachyatum, Rhizopus nigricans, Cylindrocarpon radicicola, Neurospora crassa, Botryodiplodia theobromae, Bacillus subtilis, Bacillus cereus, Erwinia carotovora and Serratia marcescens. Some of these microorganisms are transient invaders. Of the calcium-based chemicals used to prevent mouldiness, only CaCO3 and Ca(OH)2 proved effective and also prevented infestation of the chips by storage pests throughout the period of study. Whereas the product of the untreated yam chips was preferred in terms of colour, the product of CaCO3- and Ca(OH)2- treated yam chips were preferred in terms of taste and texture. As for physiological reaction after eating the products of the treated chips, Ca(OH)2- treated chips seemed to be more preferred by the members of the tasting panel.