This New Zealand population based study used a lifetime occupational history to examine occupational risks for four different measures of chronic obstructive respiratory disease using lifetime occupational histories and self reported occupational exposures the main limitations of this study are the relatively small numbers in some of the occupational groups reducing our power to detect associations the large age range of our population also meant that we had fewer individuals in the older age groups and does not usually present until late middle age or old age in addition there was possible bias from selection and reporting the healthy worker effect and job selection as well as possible error from multiple comparisons.