The diagnosis of blood-borne viral infection amongst drug injectors in Wales is limited by a poor uptake of diagnostic testing; recent research suggests that dried blood spot (DBS) sample collection, rather than venepuncture, may improve diagnostic rates. We carried out an audit of the uptake of DBS testing for hepatitis C, hepatitis B and HIV amongst drug injectors attending a substance misuse service (SMS) in the first year of DBS testing being routinely offered to clients (1 May 2007 to 30 April 2008) and compared the uptake to venepuncture testing of SMS clients in the previous year. Uptake of DBS testing for hepatitis C, hepatitis B and HIV was almost six times greater than the uptake of venepuncture testing amongst clients of the SMS in the previous year. The data are consistent with the hypothesis that DBS testing can increase the uptake of blood-borne viral testing amongst current and ex-drug injectors. We accept that part of the almost sixfold increase in diagnostic testing observed in the first year of DBS testing may be due to an increase in awareness amongst drug injectors of testing opportunities and a prioritization of testing by the SMS. Nonetheless the dramatic increase in uptake demonstrates that DBS testing is acceptable to drug injectors and should be subject to more rigorous trials to evaluate its potential impact on diagnosis.