This paper analyzes data from 13 third-generation fiberglass sucker rod strings in Andrews, Ector, and Winkler counties from Jan. 1978 to June 1979. Composition of the rod strings ranged from 31 to 90% fiberglass. Pumping depths range from 4,000 to 10,300 ft. Proper application can Pumping depths range from 4,000 to 10,300 ft. Proper application can increase efficiency in terms of energy expended per barrel of crude lifted when compared to steel sucker rods. Introduction Development of fiberglass sucker rods for use in beam-pumped oil wells started in 1973, based on the need for a sucker rod that could pump under highly corrosive and heavily loaded conditions.Currently, evaluation of the third generation of fiberglass sucker rods is being performed by the industry. This generation of fiberglass sucker rod strings are being used in beam-pumped oil wells where economic situations justify their use. They are not likely to replace totally the mainstay of beampumping - steel sucker rods.Three criteria were developed to compare and evaluate fiberglass sucker rod performance with steel sucker rods:total fluid production,failure frequency, anddynamometer-peak torque analyses. Each of these criteria was investigated in depth and evaluated for each well. The combined results determined the classification of either success or failure for each installation. Assumptions and Qualifications 1. This study concerns only data from the Andrews Dist. of Amoco Production Co. in the west Texas counties of Andrews, Ector, and Winkler. 2. Economics were the determining factor for each installation, but the economic goals varied. The desired goals were either increased production or reduced rod failures. The primary goal of each installation was the focal point of the evaluation on each well, as long as the other two areas performed satisfactorily. 3. Manufacture of fiberglass pony rods was discontinued in Feb. 1979 because of a high incidence of unexplained partings. Although 11 failures of this type are included in the analysis, they will not be a factor in future installations. Currently, all fiberglass pony rods in the district have been replaced by steel pony rods in the district have been replaced by steel pony rods. pony rods. 4. All 13 fiberglass sucker rod strings discussed here were produced by the original manufacturer (Joslyn Manufacturing and Supply Co.) and are third-generation rods. Manufacturing Process for Third-Generation Rods The manufacturing process is composed of the pultrusion and end fitting process. The pultrusion pultrusion and end fitting process. The pultrusion process has not changed conceptually since a process has not changed conceptually since a previous report, except that the looping of glass previous report, except that the looping of glass fibers has been eliminated. The pultrusion process uses approximately 150 rovings of glass filaments per rod. Each is composed of thousands of glass filaments. More than 1.5 million individual glass filaments, each 15 microns in diameter, are wetted with a thermosetting resin and then pulled through a heated forming die. JPT P. 1339