Objectives: Many local governments are trying to establish health in all polices (HiAP), but no sensitive tool is available to measure HiAP growth processes. This study explores the applicability of a general maturity model to classify stages of HiAP and to characterize its manifestations and conditions. Methods: Based on other maturity models we have developed a maturity model for HiAP (MM-HiAP), which consists of six maturity levels and 14 corresponding key characteristics. This model was applied to assess HiAP growth processes within 16 municipalities in the Netherlands. We used municipal policies on health inequalities as a case. Empirical data was gathered based on document analysis, a questionnaire and interviews. Results: Using this model we were able to classify HiAP growth processes by several characteristics, such as the recognition of the importance of HiAP (Stage I; four municipalities), HiAP described in policy documents and collaboration with sectors present (Stage II; seven municipalities), concrete collaboration agreements and structural consultations forms (Stage III; four municipalities), and a broad, shared vision on HiAP (Stage IV; two municipalities). Examples of necessary conditions were sufficient support and resources. Conclusions: This study shows that it is possible to apply a maturity model to classify stages of HiAP in municipalities. Use of the MM-HiAP as a formal measuring instrument depends on further operationalization and validation. © 2013 Elsevier Ireland Ltd.