Objective: To examine the knowledge, approaches and attitudes of fitness instructors dealing with clients seeking weight loss advice. Design: A qualitative project whereby semi-structured interviews were conducted with ten fitness instructors representing a range of qualifications, work settings and years of experience. Setting: Interviews were conducted at neutral sites identified by participants. Methods: Interviews explored participants' knowledge on weight related issues including the etiology and consequences of obesity, the exercise strategies used for weight loss, and also professional development issues. All interviews were audio taped and transcribed verbatim. Data were analysed using an inductive process where ideas of a similar nature were categorised into "raw themes". Two researchers independently analysed transcripts to establish trustworthiness. Results: Findings revealed that inconsistencies appeared to exist with participants' development and delivery of a weight management programme. In some cases fitness instructors were not adequately prepared for dealing with overweight and obese clients. Conclusion: The findings provide further argument for the need for a system of accreditation of fitness instructors within New Zealand (NZ) that provides the public with some measure of quality assurance. (Contains 1 table.)