Positive ion composition measurements in the D and E regions were performed on three rocket flights during the 1966 solar eclipse program conducted at Cassino, Brazil. The E region results showed that, at totality, NO+ and O2+ decreased in density while the ratio NO+/O2 increased. Long-lived meteoric ions appeared to be unaffected during the short period of the eclipse. A submerged layer of meteoric ions became prominent at totality when the molecular ion densities were smallest and produced a sporadic E layer. The D region results indicated that the decay in the water cluster ions at totality was probably less than a factor of four in the vicinity of 80 km. This work represents part of a continuing Air Force program to study lower ionospheric processes which affect communications. (Author).