The purpose of our reconnaissance surveys made in July 1965, August and November, 1966, and briefly in August 1969, was to determine the character of the flora of the pajonales as well as to examine the ecological factors which contribute to the occurrence, distribution, and stability (or instability) of the vegetation. The study was conducted as part of a larger survey of the natural and cultivated savannas and grasslands of eastern Peru and their potential for supporting cattle ranching (Denevan and Chrostowski, n.d.). More detailed field work in the Gran Pajonal was planned but we were unable to carry it out; hence, there are significant inadequacies in the present report, particularly in regard to soils.