Abstract The results are given of experiments on the nonaseptic, high-temperature production of a fungal biomass from cassava ( Manihot esculenta Crantz). The experiments were conducted at the pilot plant level at CIAT, using the fungus Aspergillus fumigatus I-21A as a second stage in the evaluation of the technology developed and tested previously on a laboratory scale at the University of Guelph. A brief description of the process and a schematic representation of the different steps required at this level are included. The substrate employed was grated fresh cassava roots from several low-cyanide cultivars with a total quantity utilized of approximately 425 kg of cassava per fermentation. The initial concentration of carbohydrates in the culture medium was adjusted to 40 g l −1. The fungus used is characterized by its ability to grow at very low pH (3.5) and reasonably high temperature (45°C), selective growth conditions which appear to obviate the need for sterilization and maintenance of aseptic conditions. The protein yields reported were not as high as obtained in previous small-scale fermentations, with the total crude protein content of the final product averaging < 35% of dry matter. This was partially due to an incomplete utilization of carbohydrates. The quality of the tap water as related to pH of the culture medium might also have had some adverse effect on the growth of the micro-organism. While the protein of the final product was low in sulphur-containing amino acids, particularly methionine, its amino acid profile compared favorably with that of other protein sources. The results obtained to date suggest that single-cell protein (SCP) production from cassava may have potential for practical application in cassava producing areas provided safe operational procedures can be established.