The informal sector is active in the collection, processing and trading of recyclable materials in urban China. Formal waste management organisations have established pilot schemes for source separation of recyclables, but this strategy is still in its infancy. The amounts of recyclables informally picked out of the municipal solid waste stream are unknown as informal waste workers do not record their activities. This article estimates the size and significance of the current informal recycling system with a focus on the collection of recyclables. A majority of the reviewed literature detects that official data is displaying mainly 'municipal solid waste collected and transported', whereas less information is available on 'real' waste generation rates at the source. Based on a literature review the variables, the 'number of informal waste workers involved in collection activities', the 'amounts collected daily per informal collector' and the 'number of working days' are used to estimate yearly recyclable amounts that are informally diverted from municipal solid waste. The results show an interval of approximately 0.56%-0.93% of the urban population or 3.3-5.6 million people involved in informal waste collection and recycling activities in urban China. This is the equivalent to estimated informal recycling rates of approximately 17-38 w/w% of the municipal solid waste generated. Despite some uncertainties in these assessments, it can be concluded that a significant share of recyclables is collected and processed by informal waste workers.