A production scale, natural convection, wood fired dryer for cocoa was tested during the six month period of the 1978 cocoa harvest in the Bahia region, Brazil. The object of the test sequence was to determine and investigate the operational parameters of the drying unit with a view to the subsequent development of improvements which could be applied in the field to the existing 25 000 dryers of this type. The design of dryer used was, for the most part, that recommended by the Extension Department of CEPLAC, while care was taken to ensure that the operational procedure was as near as possible to that normally used on farms. The performance of the dryer with different cocoa and wood loadings and with varying plenum chamber heights was investigated. The effect of ambient wind speed and direction was also considered.