Adherence to the street gang culture is often presented as an explanation for the high propensity for delinquency of the offenders associated with these groups. However, few people have specifically addressed the operationalization of this concept. The objectives of this article are to define the gang culture, describe its components and propose a system of measurement for adherence to the gang culture. First, the article presents a review of the literature on the street gang culture. We propose a definition and an operationalization of the concept of gang culture. Then, the article presents the development process for a measure of adhesion to the gang culture (MACg). Finally, the article reports preliminary data of the MACg which was administered to 204 juvenile and adult offenders. The analysis results of Cronbach’s alpha coefficients and corrected item-total correlations reveal that the MACg has good internal consistency. A measure of adherence to the gang culture has numerous uses. On the one hand, it helps resolve methodological and conceptual problems affecting the study of gang influence on criminal behaviour. On the other hand, it can help improve the assessment practices of offenders involved in gang activities.