Recent developments in instrumentation for ultraviolet resonance Raman (UVRR) spectroscopy and its application to proteins are reviewed. With excitation near the ∼ 195 nm amide π-π* transition strong enhancement is seen of the amide vibrational modes, particularly amide II, whose intensity is sensitive to secondary structure. With measurements at 200 and 192 nm one can calculate the fractions of α-helix, β sheet and unordered segments from the known cross sections of these structures. The proline imide II band at ∼ 1460 cm −1 is strongly enhanced with 218 nm excitation and its frequency can be used to monitor cis-trans isomerization. Aromatic residues give rise to strong UVRR bands. Phenylalanine (Phe) and tyrosine (Tyr) show scattering patterns typical of substituted benzenes: enhancement of vibronic modes, especially ν 8a and ν 8b in resonance with the quasi-forbidden L a transition (∼ 205 and ∼ 223 nm for Phe and Tyr), and of breathing modes in resonance with the allowed B a,b transitions (∼ 188 and ∼ 193 nm for Phe and Tyr). Tyrosine, and especially tyrosinate, also show strong enhancement of ν 8a and ν 8b in the B a,b-resonant region, behavior attributed to electronic mixing of L a with B a via the OH (or O −) substituent. In proteins the Tyr ν 8a and ν 8b bands are most readily observed with 229 nm excitation, where the Phe contributions are minimal. The ν 8b frequency is sensitive to Tyr H-bonding and has been calibrated in terms of the H-bond strength. The Tyr 830/850 cm −1 Fermi doublet intensity ratio, which can be monitored at 200 nm is sensitive to H-bonding, but also to other environmental influences. With 218 nm excitation protein spectra are dominated by tryptophan (Trp) contributions. The 1340/1360 cm −1 Trp Fermi doublet is sensitive to solvent exposure, while the ∼ 880 cm −1 band frequency is sensitive to H-bonding. Histidine (His) excitation profiles show π-π* resonances at ∼ 218 and ∼ 204 nm. The UVRR bands are sensitive to protonation, but the enhancement is relatively weak, and the His bands are obscured in protein UVRR spectra by the other aromatic contributions. Applications of the UVRR technique to the filamentous virus fd are described.