This review discusses the use of synchrotron X-ray and high-flux neutron beams in biology. Particular highlights of recent work include (a) the ability to survey usefully and comparatively the solution properties of several of the complement components of immune defence; (b) the monitoring of the allosteric properties of aspartate transcarbamoylase in solution; (c) the kinetic study of the assembly and disassembly of tubulin protofilaments and virus capsids under a range of conditions; (d) the dissection of glycoproteins, membrane protein-lipid complexes, chromatin, ribosomes and viruses in terms of distinct internal structural regions of differing chemical compositions; (e) the location of the 21 proteins of the 30 S ribosomal subunit by deuteration and label triangulation.