The high-resolution infrared spectra of the v(1) + v(3) (2CH) band of the Ar-C2H2 complex has been recorded from 6544 to 6566 cm(-1). The previously reported K-a = 1 <- 0, 2 <- 1, and 0 <- 1 subbands were observed and the K-a = 1 <- 2, 2 <- 3, and 3 <- 2 subbands were assigned for the first time. The intermolecular potential energy surface of this complex has been calculated ab initio and optimized by fitting the new high-resolution data. Refined intermolecular potential energy surfaces have been obtained for the ground vibrational state and for the excited v(1) = v(3) = 1 stretching state. For the former state, the results of the analysis are satisfactory and the microwave transitions of the complex are reproduced with a root-mean-square deviation of 5 MHz. For the latter state, systematic discrepancies arise in the analysis.