Ion mobility and mass spectrometry techniques have been used to study clusters of serine formed by sonic spray ionization. Broad distributions of cluster sizes and charge states are observed, ranging from clusters containing only a few serine units to clusters that contain more than 600 serine units (i.e., protonated clusters of the form [mSer + nH](n+) with m = 8 to >600 and n = 1 to 10). Experimental collision cross sections, derived from the mobility data, are dependent upon cluster size but are not significantly influenced by the cluster charge state. A comparison of calculated cross sections for different trial geometries for several cluster sizes indicates that large clusters adopt tightly packed, roughly spherical geometries. The most abundant cluster size in the spectrum corresponds to the [8Ser + H](+) cluster; however, this ion comprises less than 1% of the total serine abundance. The measured cross section, Omega([8Ser + H](+)) = 190 Angstrom(2), is in good agreement with the 191.2 +/- 0.2 Angstrom(2) value reported previously from electrospray ionization. Isotopic labeling studies indicate that [8Ser + H](+) retains a strong chiroselective preference. Evidence for some chiroselectivity in larger clusters is presented.