Purpose: The aim of this study was to determine the role of qualitative histological interpretation of the prostate gland in predicting the clinical outcome of terazosin therapy. Patients and Methods: Thirty-six male patients with symptomatic benign prostatic hyperplasia (BPH) and with a serum PSA 4-10 ng/ml underwent transrectal prostate ultrasonography and biopsy prior to terazosin therapy. Histological sections were stained with hematoxylin-eosin. A qualitative conventional light microscopic analysis (CLMA) and then color-assisted quantitative morphometric image analysis (MA) of the specimens were done. Results of these two techniques (CLMA and MA) were interpreted according to terazosin theraphy results. Results: When CLMA was used, 50% or more stromal content was significantly related to the percent change of urinary flow rate (Qmax) but not with International Prostate Symptom Score (IPSS) after the terazosin therapy. Similarly, MA results showed a significant relationship between the percent of stroma and the percent change of Qmax, but not with the percent change of IPSS after the terazosin therapy. Conclusion: Qualitative CLMA or quantitative MA of BPH tissue composition can be used in predicting clinical outcome of terazosin therapy, but it is suitable only in patients for whom prostatic biopsy is inevitable in order to rule out prostate cancer.