The ovipositional behaviour of the mirid predator Macrolophus caliginosus Wagner, a potential biological control agent of glasshouse pests, was studied in detail using a modified video camera technique. In the laboratory, females laid their eggs in the leaves of tobacco plants. They remained generally motionless on the main veins of the leaves, raised their body, folded the rostrum towards the thorax and extended their ovipositor when selecting a site in which to oviposit. The ovipositor was inserted into the plant tissue by a downward and forward thrust of the body and contractions of the abdominal muscles. After a period of immobility, the ovipositor was retracted and the insect's body and organs returned to their initial positions. This behaviour was preceded and followed by extensive rostral exploration of the oviposition site. In most females the same area was explored before and after egg-laying and the ovipositor was inserted approximately in the middle of the selected area. The sequence and pattern of ovipositional behaviour varied between females.