Letter from Dr J Smith, Plasma Fractionation Laboratory, to Dr B Colvin, The London Hospital, regarding surveillance for evidence of any NANBH transmission by BPL concentrates 8Y and 9A. Encloses a report entitled,Surveillance of Non-A Non-B Hepatitis Transmission by coagulation Factor Concentrated, Dry Heated at 80 C, by the Study Group of the UK Haemophilia Directors on Surveillance of Virus Transmission by Concentrates