There was a severe earthquake at the Koyna Dam on December 11, 1967, with its epicenter very close to the dam site. The higher monoliths of the dam suffered significant damage during the earthquake. In order to corroborate the observed behavior of the dam with its behavior anticipated theoretically, the highest monolith of the dam has been analyzed due to the actually recorded ground motion during this earthquake. The theoretical analysis indicates the zones of maximum tensile stresses which coincide with the location of cracks in the dam monolith confirmed by observation after the earthquake. The maximum tensile stresses in these zones are found to be higher than the ultimate tensile strength of the dam material and thus cracking is expected in these regions. The theoretical techniques of analysis thus adequately explain the distressed behavior of the dam and can confidently be applied to predict the performance of dams during future earthquakes.