The structures and the vibrational spectra of cyanoacetylene clusters were investigated with the aid of ab initio Moller-Plesset second-order calculations using large polarized basis sets. In addition to ring- and chainlike structures, stacked non-hydrogen-bonded configurations, in which chainlike oligomers are oriented in an antiparallel fashion, were investigated. Particular emphasis has been given to a more thorough investigation of selected sections of the energy surface of the cyanoacetylene dimer, including the search for parallel and antiparallel stacked structures and for pi-type hydrogen-bonded configurations. This search revealed that apart from the linear dimer which corresponds to the energetically most stable dimer, a second minimum corresponding to a C-2h stacked antiparallel dimer is quite close in energy, whereas pi-type hydrogen-bonded configurations and parallel but slipped stacked arrangements are barely bound. The relatively high stability of the antiparallel stacked dimer has the consequence that larger stacked clusters, e.g., tetramers and hexamers, are Likely to be of similar stability as the corresponding cyclic oligomers or are even the dominant species and that both, stacked and cyclic configurations, are significantly more stable than linear clusters from the tetramers on. Most of the experimentally observed infrared-active C-H stretching frequencies could be successfully assigned to particular oligomers.