The emergence of the fields of wearable devices, e-textiles and smart packaging brings new requirements on electronics and sensing systems. One or a combination of the following properties can be desired for their proper operation and to meet the functionalities required by the application in order to improve market penetration. Very low-cost, thin, large area, lightweight, flexibility, conformability, transparency, stretchability are some of the characteristics that can be offered by making sensors on polymeric foil. We propose printing processes for the fabrication of these devices to mainly reduce their production cost and to improve the environmental friendliness of their manufacturing. In this communication, we discuss the benefits, drawbacks, potential, and challenges of printing sensors on plastic substrates illustrated with some examples of technical developments performed in our laboratory. We present environmental sensors fabricated on plastic foil and the associated flexible encapsulation method at the foil level. Integration of printed sensing devices on smart RFID tags is also discussed. By using thin polymeric substrates, very small bending radius of curvature can be achieved. Besides the challenges linked to the large area printing of the sensing devices on flexible foil and the reliability of these devices under mechanical cycling, new developments are required on the interconnectivity of these devices with other electronics components to achieve efficient system integration. (C) 2011 Published by Elsevier Ltd.