A random walk on the PES for (MeSH)4 clusters produced 50 structural isomers held together by hydrogen-bonding networks according to calculations performed at the B3LYP/6-311++G** and MP2/6-311++G** levels. The geometric motifs observed are somewhat similar to those encountered for the methanol tetramer, but the interactions responsible for cluster stabilization are quite different in origin. Cluster stabilization is not related to the number of hydrogen bonds. Two distinct, well-defined types of hydrogen bonds scattered over a wide range of distances are predicted.