We describe a new magic angle spinning (MAS) NMR experiment for obtaining N-15-N-15 correlation spectra. The approach yields direct information about the secondary and tertiary structure of proteins, including identification of alpha-helical stretches and interstrand connectivity in antiparallel beta-sheets, which are of major interest for structural studies of membrane proteins and amyloid fibrils. The method, N-15-N-15 proton assisted recoupling (PAR), relies on a second-order mechanism, third spin assisted recoupling (TSAR), used previously in the context of N-15-C-13 and C-13-C-13 polarization transfer schemes. In comparison to N-15-N-15 proton-driven spin diffusion experiments, the PAR technique accelerates polarization transfer between N-15's by a factor of similar to 10(2)-10(3) and is furthermore applicable over the entire range of currently available MAS frequencies (10-70 kHz).