We have measured the charge distributions of background developed toner to get a picture of the underlying mechanism of background development in two-component development process.Polycarbonate films containing molecularly dispersed charge transporting material were used as a model of photoreceptor. Positive charged toner was developed onto the model photoreceptor using a practical analogue copier machine without charging process, which was corresponding to the background development in the practical photography process.It was found that a charge distribution curve of background toner had two peaks assignable to low-charged wrong sign toner and high-charged right sign toner, respectively. The peak of high-charged right sign toner was observed to coincide with the peak of toner in a developer. Another peak was found to appear around 0fC/μm.The pattern of charge distribution curves for background developed toner was able to be classified into two types according to the type of toner. One was such that the amounts of high-charged right sign toner was dominant. And the other was that the amounts of low charged toner was a major component.Moreover, the peak of high-charged right sign toner particles was selectively reduced by the addition of lubricant to photoreceptors. This result suggests that the background deposition of high-charged right sign toner was primarily caused by the adhesion force of toner particle to the photoreceptor.