The seismic performances of one control and three retrofitted half-scale circular reinforced concrete columns were studied. The columns were 10 ft high, 18 in. in diameter, fixed at the base, and free at the top. An axial, vertical load of 158 kips was applied at the top, which was translated horizontally in a plane symmetrically about the vertical in such a way as to produce a maximum of four times the yield strain in the longitudinal reinforcing steel at the extremes of the first cycle. The columns were then oscillated between these extreme displacements of the first cycle until the lateral forces required to produce these translations approached zero. The measure of seismic durability used was the number of such cycles that a column sustained before losing structural integrity. The four columns were all made at the same time with 3,200-lb/sq in. concrete and the same reinforcing and ties. The arrangement was intended to model that of bridge columns of the 1960s. Three columns were retrofitted with prestressed, externally located circular ties at intervals along the lower 3 ft. The spacing and size of these ties varied from column to column. The control column sustained less than one cycle before losing structural integrity; the retrofitted columns sustained a minimum of 13 cycles.