Evaluation is a systematic assessment against standards, which can ascertain the degree/value of achievement, help in decision-making, enable reflection, and enable future changes. Different levels of evaluation may be considered including technical, process, economic, social, and political elements according to the needs and purpose of evaluation. In any evaluation process, one should always consider the point of view taken, the timing of evaluation, the period under evaluation, and the level of evaluation. This chapter presents some theoretical concept of evaluation ideology and reviews the different types of evaluation available in the literature and how they can be applied to evaluate animal health surveillance systems.