Steroidal 5α-reductase is a NADPH dependent enzyme that catalyzes the irreversible conversion of 4-en-3-oxo-steroid testosterone to the corresponding 5α-H-3-oxo-steroid dihydrotestosterone thus involved in Benign Prostatic Hyperplasia (BPH). As the crystal structure of target enzyme is not available; we have carried out ligand based designing using Self Organizing Molecular Field Analysis (SOMFA). SOMFA, a novel 3D-QSAR methodology used in present case to study the correlation between molecular properties and human 5α-reductase inhibitory activities of a series of unsaturated 3-carboxysteroid. The statistical results, good cross-validated r²_cv (0.693) and non cross-validated r² (0.732), showed satisfied predictive ability. All analysis of SOMFA model may provide some useful information in the design of human steroidal 5α-reductase inhibitors with better spectrum of activity.