We used the MembStruk computational procedure to predict the three-dimensional (3D) structure for the serotonin 5-HT(2C) G-protein-coupled receptor (GPCR). Using this structure, we used the MSCDock computational procedure to predict the 3D structures for bound ligand-protein complexes for agonists such as serotonin and antagonists such as ritanserin, metergoline, and methiothepin. In addition, we predicted the SAR data for a series of psilocybin analogs, both agonists and antagonists. We performed molecular dynamics (MD) on serotonin bound to 5-HT(2C) and we find the protein and binding site to be stable after 5ns. We find good agreement with the currently known experimental data and we predict a number of new mutations which could be used to validate further our predicted structures. This agreement between theory and experiment suggests that our 3D structure is sufficiently accurate for use in drug design. We also compare a preliminary prediction for 5-HT(2B) with our prediction for 5-HT(2C) and find a difference in TM5 that contributes to different serotonin binding modes in 5-HT(2B) and 5-HT(2C).