Debates about Britain's productivity performance have often drawn attention to the roles played by working practices and employment relations. In the 1980s and 1990s, trade unions were a prime focus; more recently, attention has turned to high-involvement management (HIM) practices (also referred to as ‘high-performance work systems’). We combine the two to investigate the relationships between work organisation, trade union representation and workplace performance. We find that HIM has a positive impact on labour productivity. However, this effect is restricted to unionised workplaces, and seems more readily explained by concessionary wage bargaining than ‘mutual gains’, given the absence of any association with financial performance. These findings raise questions about the universal applicability of HIM as a route to improved workplace performance.