Municipal transparency in AbstractIntroduction. This article aims to determine the most influential factors in the degree of transparency of Spanish municipalities, according to the Municipal Transparency Index (ITA). In particular, the study focuses on the detailed analysis of four possible factors of influence: political party, number of inhabitants, geographical location, and level of per capita income of the municipality. The conclusion is that, at the moment, and given the evolution of this Index, none of the previous factors constitutes a determinant in the degree of transparency. In order to carry out a more extensive and precise analysis it would be necessary to expand the methodological procedures followed by the Municipal Transparency Index (ITA) and include new factors of study. Methods. The study is based on literature review, in-depth interviews with a panel of experts and the study of the factors that influence the most the degree of municipal transparency. Results and conclusions. The progress experienced in municipal transparency is significant but it would be advisable to also evaluate and improve the procedures used to calculate the Municipal Transparency Index (ITA).