Effective treatment of benign prostatic hyperplasia (BPH) improves lower urinary tract symptoms (LUTS) and patient quality of life, and reduces the risk of complications arising from disease progression. However, treatment can only be initiated when men with BPH are identified by accurate diagnostic tests. Current evidence suggests that diagnostic procedures employed by primary care physicians vary widely across Europe. The expected increases in BPH prevalence accompanying the gradual aging of the population, coupled with greater use of medical therapy, mean that general practitioners (GPs) are likely to have an increasingly important role in managing the condition. The GP/primary care clinic is therefore an attractive target location for strategies designed to improve the accuracy of BPH diagnosis. The Diagnosis Improvement in Primary Care Trial (D-IMPACT) is a prospective, multicentre, epidemiological study that aims to identify the optimal subset of simple tests applied by GPs in the primary care setting to diagnose BPH in men who spontaneously report obstructive (voiding) and/or irritative (storage) LUTS. These tests comprise medical history, symptom assessment with the International Prostate Symptom Score questionnaire, urinalysis, measurement of serum levels of prostate-specific antigen and subjective GP diagnosis after completing all tests including digital rectal examination. GP diagnoses and all other tests will be compared with gold-standard diagnoses provided by specialist urologists following completion of additional diagnostic tests. D-IMPACT will establish the diagnostic performance using a non-subjective and reproducible algorithm. An adjusted and multivariate analysis of the results of D-IMPACT will allow identification of the most efficient combination of tests that facilitate accurate BPH diagnosis in the primary care setting. In addition, D-IMPACT will estimate the prevalence of BPH in patients who present spontaneously to GPs with LUTS.