The photoassociation of colliding ultracold trapped atoms permits the observation of high resolution molecular spectra of high lying vibrational levels with low total angular momentum and outer turning points greater than 50 Angstrom A. This paper describes how the hyperfine structure of alkali dimer molecules at large internuclear separation can be used to assign the electronic character of the observed photoassociation spectra and how hyperfine structure helps to explain the observed photoassociation spectrum of the attractive electronic states of the Na-2 molecule that correlate with Na(3 S-2)+Na(3 P-2(3/2)) atoms.