The Fourier transform infrared spectrum of the nu5 band of deuterated formic acid (DCOOH) has been measured with a resolution of 0.004 cm-1 in the frequency range of 1090-1180 cm-1. Using a Watson's A-reduced Hamiltonian in the Ir representation, a total of 1731 assigned unperturbed transitions have been analyzed to provide rovibrational constants for the upper state (v5 = 1) with a standard deviation of 0.000363 cm-1. The band is A type with an unperturbed band center at 1142.31075 +/- 0.00002 cm-1. The band is expected to be perturbed by a nearby nu4 band through a Fermi resonance term and possibly a Coriolis term. The resonance is particularly noticeable for Ka = 10, and 11, at high J values. About 215 perturbed lines were identified but they were not included in the final fit. Copyright 1998 Academic Press.