BACKGROUND The prognostic value of serum total testosterone (TT) prior to treatment has not been investigated. OBJECTIVE This study was performed to determine how baseline TT influences changes in body composition in men undergoing testosterone therapy (TTh). METHODS Response to TTh in a clinical population of men with symptomatic testosterone deficiency (TD). METHODS Retrospective case series of 58 men with TD were treated with TTh. All were naïve to previous TTh. Men were stratified into two groups: group 1 (N = 38) consisted of men with baseline TT > 300 ng/dL (10.4 nmol/L) and group 2 (N = 20) consisted of men with total TT < 300 ng/dL. Men in group 1 were diagnosed with TD on the basis of low values of free testosterone (FT) < 1.5 ng/dL (19.3 pmol/L). Dual-energy X-ray absorptiometry was performed at baseline and follow-up (6.9 ± 4 months) to assess regional and whole body. RESULTS At baseline, both groups had similar lean mass (LM) and fat mass (FM), but percentage of trunk FM and percentage of total FM were significantly higher in group 2. Both groups demonstrated similar increases in LM for arms, legs, and total body. Percentage of total FM significantly decreased in both groups. CONCLUSIONS Baseline severity of symptomatic TD influences body composition. Similar changes in LM and FM were seen with TTh regardless of baseline severity in TD. Men with TT > 300 ng/dL demonstrated significant positive changes in body composition. The similarity in objective response to TTh in these two groups provides support for the value of FT in the assessment of men with symptoms suggestive of TD.