An eastern gorilla group of the Mt. Kahuzi region (République du Zaire) was studied over 15 months. Its migration route was determined, and the various biotopes it visited are described. A record was made of its main food plants, and of the plant parts eaten. For nine important food plants the protein content, the concentration of the individual amino acids and the water content were measured for the plant parts eaten and for those not eaten. For some of these plant parts the Na, K, Ca and Mg content were also determined. No general correlation between food selection and one or several of these factors could be found. The development and value of a traditionally determined mixed diet is discussed