The synthesis and characterization of phenylethanethiolate-coated monolayer protected clusters (MPCs) with Au-140 (average) and Au-38 cores are described. The latter 1.1 nm core diameter nanoparticles, whose Au-38(PhC2S)(24) composition was analytically established, are stable and isolable in relatively high purity and similar to200 mg quantities per reaction batch. Chemical shift effects in H-1 and C-13 NMR spectra reveal the existence of either closely related Au-38 structures or differences between ligands on a given structure, or both. The Au-38(PhC2S)(24) MPCs undergo place exchange reactions with other thiolate ligands and, owing to their stability and ease of production, provide a gateway to other Au-38 MPCs with partially or completely different monolayer compositions.