The electronic and vibrational spectra of organized films of N-substituted perylenetetracarboxylic monoimides (PTCOs, R = propyl, pentyl, a-phenylethyl, and 6-hydroxyhexyl) are reported. The materials were fabricated into Langmuir-Blodgett (LB) films on a variety of substrates for spectroscopic characterization. The average molecular orientation in multilayer assemblies was deduced using transmission and reflection absorption infrared (RAIR) spectroscopy. Visible absorption and emission spectra were collected to study molecular organization and aggregation in the LB films. The influence of the R groups in the formation and stability of floating layers and the effect of annealing on the LB structure was also investigated. Surface-enhanced infrared and Raman spectra of monolayers of these materials are reported here for the first time.