The aggregation of pseudoisocyanine (PIC) is of interest because of the unusual properties of the aggregates which make them useful in photographic science as sensitizers as well as in photosynthesis research as model systems. Here, the room-temperature substructure of the J-absorption band of PIC-Cl aggregates is discussed on the basis of the results from nonlinear polarization spectroscopy in the frequency domain. The results are compared with the known substructure at 4.2 K.