Secondary retention refers to cessation of tooth eruption after emergence. The aim of this study was to evaluate the clinical, radiographic, and histological characteristics of secondary retention as well as the treatment results in a group of thirty-four patients with seventy-seven secondarily retained primary molars. The most important clinical and radiographical criterion for diagnosing secondary retention was infraclusion. Percussion was not a reliable diagnostic tool. Secondary retention in the primary dentition may predispose to a similar disorder in the permanent dentition. In many cases, occlusal disturbances and underdevelopment of the alveolar process disappeared spontaneously after eruption of the permanent successor, unless a similar disorder was observed in the permanent dentition. Active therapy is necessary only in case of severe infraclusion, severe malocclusion, dislocation or agenesis of the successor.