The 1996 edition of the British Standard BS 6399-1, ’Loading for buildings, Code of practice for dead and imposed loads’, included guidance on dynamic loads generated by synchronized crowd movement. This Digest provides information that explains and supports the recommendations in the Standard, and provides a method for calculating structural response to rhythmic crowd loads. This edition of Digest 426 supersedes the version published in 1997. It includes improved information on the loads generated by crowds. 12 pages.