The thesis aims to explain increasing accountability in the French nonprofit sector. The qualitative research investigates the hypothesis that engendering trust is the key rationale for increasing accountability. The research also explores inductively other potential rationales for increasing accountability (e.g. corporatisation, integration of international standards of accountability, donor pressure, and the media). US regulatory, self-regulatory, and voluntary models of accountability provide reference standards. The study targets 45 renowned French NPOs. 33 are members of a national independent accountability accreditation organisation (Comite de la Charte de Deontologie), and 12 comprise a control group. The driving voice is the perspective of the most senior leaders of respondent organisations, almost all executive directors, board Presidents, or board members. The theoretical framework centres on Henry Hansmann's theory of trust (derived from legal restrictions on profit distribution or the "nondistribution constraint') as an explanation for the origin and on-going efficacy of the nonprofit form. First establishing the relevance of Hansmann's demand side theory in France, the analysis then bridges Hansmann's rationale for the nonprofit organisational structure to analysis of how and why French NPOs supplement the intrinsic characteristics of that structure with accountability. Hansmann might call this organisational effort the "supply side." Finally, the emerging spectrum from Hansmann's trust to Lester Salamon's suggestion that accountability is the modern foundation for trust because the nondistribution constraint no longer suffices also frames the analysis. The proposed definition of accountability combines a general definition and an operationalised definition (derived from scholarly literature and best practice, respectively). The analysis highlights organisations' strategic assessment of quantitative/non-quantitative considerations in accountability-related decisions, including the impact of specified internal organisational variables and external contextual variables. The most oft-cited rationale for increasing accountability is ethical, effective management, followed by donor trust. Donor trust proves essential and fragile - irrespective of cited rationale for increasing accountability