Synchrotron radiation sources are now used widely in the determination
of macromolecular structures. About a dozen beamlines are currently i
n use at existing facilities, and others are either under development
or planned at both existing storage rings and at third-generation stor
age rings. Recent results provide insights into the wide range of appl
ications of synchrotron radiation in the field of macromolecular struc
ture. Further growth in synchrotron-radiation research will depend on
the development of user-friendly facilities that allow for efficient u
se of these unique X-ray sources.