Sequential analyses of the major workplace data sets available to British researchers – the Workplace Industrial/Employee Relations Surveys (WIRS/WERS) – have revealed shifts in some previously solid relationships between union presence and a variety of establishment performance indicators. So much so that it is now conventional to speak of a pronounced reduction in the 'disadvantages of unionism' in that country. One finding that seems to have persisted in cross section, however, is the negative effect of unions on employment growth. Following on a recent study of AWIRS (Wooden and Hawke, 2000), we reexamine the issue using new panel data from the WERS series, where workplaces were surveyed in 1990 and then followed-up in 1998. We report similar evidence of employment retardation in union regimes. Moreover, use of the panel also hints that some other unfavorable union effects may be longer standing than suggested in cross-section work.