Assessment of processes in health care is needed for the measurement of six domains of quality of care (appropriateness, security, respect and caring, availability, continuity and timeliness). We propose here a typology of care, organisational and management processes. Process indicators can be classified according to objectives of the evaluation, type of processes, concerned healthcare professionals, and stage of the process. Process assessment is hindered by two main difficulties. Due to the lack of data about processes in information systems and in medical records, specific data collection is often needed and impede the feasibility of routine evaluation. The second difficulty is related to the lack of information about the properties of the indicators, their appropriateness (capacity to infer improvement actions from the result of the indicators), their operational properties (cost of data collection and acceptability by the concerned professionals), and their measurement properties (reliability and validity). Process assessment is strongly needed because outcome assessment can be not possible or not appropriate. The lack of information about the process-outcome relationship is the major obstacle and the main contra-indication to its use. Validation of process indicators is therefore an important research area for the future.