Background
We investigated the ways in which research evidence about the health effects from secondhand smoke (SHS) and smokefree policies was publicly used or regarded by New Zealand parliamentary politicians, during efforts to strengthen a smokefree law (ie, from 1997 to 2005).

Methods
A documentary case study used published and unpublished material recording the use of research evidence by politicians. The material was collected for the period 1997-2005 from the parliamentary record, media and other databases. Additional searches were made to provide context for the politicians who used research.

Results
Major themes identified included: (a) the employment of local estimates of SHS mortality, (b) linking specific health effects (eg, cancer) to SHS exposure, (c) a focus on the use of research relevant to bar workers, and (d) the use of research to downgrade the health effects, and attacks on the credibility of research showing health effects from SHS. Almost half of the 21 Members of Parliament (MPs), who spoke in parliament about SHS research during 2000-2005, denied or were sceptical about SHS harm. At least five MPs used tobacco industry funded or disseminated versions of research. There was some indirect evidence that the degree of exposure to the health sector, or the tobacco industry and its allies, may have been factors in the use by MPs of the research. Policy implications: The willingness of some of this group of politicians to adopt tobacco industry arguments suggests possible options within health promotion. These include the better enforcement of consumer protection laws (preventing deceptive information by the tobacco industry and its allies), and the adoption of an increased focus on tobacco industry behaviour within tobacco control efforts. These moves may have beneficial effects for the use of research in public health policymaking. The strengthening by the health sector of its advocacy capacity and effectiveness may also be a crucial step in the better use of research by politicians in the policymaking process.