Currently, three farming systems for laying hens are frequently implemented in practice: Free-range farming, floor management, and small-group systems, whereby mixed forms of these housing systems are also common. In free-range systems,hens have the possibility to go outside and become exposed to natural sunlight, whereas floor management and small-group systems operate with UV-free light regimens. Therefore, we hypothesized that eggs from free-range hens might contain higher vitamin D contents than barn eggs. The present study aimed to investigate the vitamin D content of eggs in response to different housing conditions.