Testosterone (T) replacement is being increasingly offered to older men with age-related decline in testosterone levels. The effects of long-term testosterone replacement and aromatase inhibition (AI) on glucose homeostasis and cardiometabolic markers were determine in older non-diabetic men with low testosterone levels. Men 65years, mean age 71 +/- 3years with serum total T<350ng/dL were randomized in a double-blind, placebo-controlled, parallel-group, proof-of-concept trial evaluating the effects of 5g transdermal testosterone gel (TT) (n=10), 1mg anastrozole (n=10) or placebo (n=9) daily for 12months. Homeostatic Model Assessment of insulin resistance (HOMA(IR)) was the primary outcome. Secondary outcomes included OGIS in response to OGTT, fasting lipids, C-reactive protein (CRP), adipokines, and abdominal and mid-thigh fat by computed tomography. All outcomes were assessed at baseline and 12months. After 12months, absolute changes in HOMA(IR) in both treatment arms (TT group: -0.05 +/- 0.21); (AI group: 0.15 +/- 0.10) were similar to placebo (-0.11 +/- 0.26), as were CRP and fasting lipid levels. Adiponectin levels significantly decreased in the TT group (-1.8 +/- 0.9mg/L, p=0.02) and abdominal subcutaneous fat (-60.34 +/- 3.19cm(2), p=0.003) and leptin levels (-1.5 +/- 1.2ng/mL, p=0.04) were significantly lower with AI. Mid-thigh subcutaneousfat was reduced in both treatment arms (TT group: -4.88 +/- 1.24cm(2), p=0.008); (AI group: -6.05 +/- 0.87cm(2), p=0.0002). In summary, in this proof-of-concept trial, changes in HOMA(IR) AI were similar in all three groups while the effects of intervention on subcutaneous fat distribution and adipokines were variable. Larger efficacy and safety trials are needed before AI pharmacotherapy can be considered as a treatment option for low T levels in older men.