The enhanced infrared spectra of Langmuir-Blodgett (LB) monolayers deposited on rough metal island films are presented. The nature and properties of surface-enhanced infrared (SEIR)spectra are discussed and compared with those of surface-enhanced Raman scattering (SERS). The geometry and polarization properties of the SEIR experiment were investigated. For practical applications, it is shown that a single sample can be prepared to obtain SERS and SEIR spectra. The use of different metals for SERS and SEIR, in keeping with the requirement of the appropriate optical constants for electromagnetic enhancement, is also discussed.