We examined local differences in prescription pattern of home mechanical ventilation (HMV) within the homogenous health care system in Sweden. We used 6 years prospective data from the national HMV Register covering the entire Swedish HMV patient population (more than 1000 patients). The treatment prevalence of HMV in Sweden, January 1, 1996 was 6.2/100,000 and January 1, 2002 10.5/100,000 with a steady increase each year in all counties. The differences between leading and non-leading counties showed a tendency to diminish due to an increasing prescription rate in the non-leading counties. During the 6 years, the proportion of Pickwickian patients increased significantly in the country as a whole, but remained considerably and significantly higher in the leading counties, in spite of similar and temporally stable prescription criteria. Even if the evident dissimilarities in treatment prevalence may be levelling out, it will most probably do so at a level as high as or higher than today's top level of more than 20/100,000 since we found that HMV therapy was well founded also in the counties with the highest prescription rates and that the prescription rate of the non-leading counties was approaching the level of the leading counties.