BACKGROUND AND PURPOSE Experiences with the ProstaLund Feedback Treatment (PLFT) with the CoreTherm device and results from a previous positron emission tomography (PET) study suggest that the intraprostatic blood flow increases considerably during treatment in response to heat exposure. Early results with intraprostatic injection of mepivacaine epinephrine prior to PLFT have indicated greater patient comfort during treatment and shorter treatment time secondary to lower intraprostatic blood flow. In this pilot study, the effect of intraprostatic injection of mepivacaine epinephrine on intraprostatic blood flow before and during PLFT was evaluated by PET using [15O]H2O. PATIENTS AND METHODS In four patients scheduled for PLFT, a baseline value of the intraprostatic blood flow was established using [15O]H2O-PET. Thereafter, intraprostatic injections of mepivacaine epinephrine were given using a prototype of the Schelin Catheter. In two of the patients, PET was performed immediately after the mepivacaine epinephrine injections and 10 and 24 minutes after the start of PLFT. To reduce the risk of wash-out of the drug, the next two patients were examined 7 and 17 minutes after the start of PLFT but not in connection with the anethetic injection. RESULTS In patients 1 and 2, mepivacaine epinephrine decreased the prostatic blood flow. During PLFT, there was a slight increase in blood flow in patient 1 and a more pronounced increase in patient 2. In patient 3, the blood flow during treatment was almost unchanged, while it decreased in patient 4. CONCLUSIONS Intraprostatic injection of mepivacaine epinephrine may reduce, or even eliminate, the increase in blood flow that is usually seen during PLFT. The vague effect seen in patients 1 and 2 may be explained by wash-out of the drug.