: Commercial farms provide most of the egg production in Turkey, and artificial lighting in commercial poultry houses is widespread. Lighting is an essential part of the physical environmental conditions that control and regulate the health and behaviour of poultry production. It is necessary to have a proper lighting plan to provide adequate lighting in the poultry house to facilitate the daily work and to create favourable conditions for the welfare of the animals, productivity and sustainability of the production and the workers. This study aims to measure the current lighting level in a conventional cage system laying hen house in Bursa and to compare it with the calculation of the amount of lighting required in theory. The calculated lighting power per unit area is 1.6 W m-2 practical and 2.2 W m-2 theoretical. It was found that the illuminance measured with a lux meter on the cage floors was close to the theoretically calculated values. It was considered that 16 reflectors of 40 W would be sufficient according to the luminous flux method. In practice, however, it was found that 24 fluorescent lamps of 36 watts provided a lighting level close to the theoretical level. Furthermore, the significance of the differences between the measured illuminance levels between the areas (corridor and floor) and the times (seasons and months) were assessed using analysis of variance. A statistically significant difference was observed between season and day.