Background: National Health Service (NHS) trusts, which provide the majority of hospital and community health services to the English NHS, are increasingly adopting a public firm model with a board consisting of executive directors who are trust employees and external non-executives chosen for their experience in a range of areas such as finance, health care and management. In this paper we compare the non-executive directors roles and interests in, and contributions to, NHS trust boards governance activities with those of executive directors; and examine non-executive directors approach to their role in board meetings. Methods: Non-participant observations of three successive trust board meetings in eight NHS trusts (primary care trusts, foundation trusts and self-governing (non-foundation) trusts) in England in 2008-9. The observational data were analysed inductively to yield categories of behaviour reflecting the perlocutionary types of intervention which non-executive directors made in trust meetings. Results: The observational data revealed six main perlocutionary types of questioning tactic used by non-executive directors to executive directors: supportive; lesson-seeking; diagnostic; options assessment; strategy seeking; and requesting further work. Non-executive board members behaviours in holding the executive team to account at board meetings were variable. Non-executive directors were likely to contribute to finance-related discussions which suggests that they did see financial challenge as a key component of their role. Conclusions: The pattern of behaviours was more indicative of an active, strategic approach to governance than of passive monitoring or rubber-stamping . Nevertheless, additional means of maintaining public accountability of NHS trusts may also be required.