Aim: Magnetic resonance imaging (MRI) and computerized tomography (CT) are used in the diagnosis and follow-up of pituitary adenoma cases. Sometimes, these methods cannot display the post-operative residual tissue. It has been shown that some radionuclides were taken up by the pituitary adenomas. The aim of this study was to evaluate the uptake of the technetium-99m (Tc-99m) tetrofosmin (TF) in the pituitary adenoma and normal pituitary tissue and assess the ability of Tc-99m TF to predict tumor malignancy in pituitary gland. Methods: The patients with pituitary adenoma (7 invasive and 8 non-invasive) were compared with control group (no. 13). Single-photon emission computed tomography (SPECT) imaging of pituitary gland was performed in both groups. Tc-99m uptake indices were evaluated statistically with the use of Mann-Whitney U test. Results: The average tetrofosmin uptake index of pituitary adenoma is 2.44 +/- 1.54 for the patients and 1.69 +/- 0.71 for the control group. Any significant difference was not observed between the groups (p 0.3). The average index was calculated as 3.04 +/- 2.15 for invasive adenomas and 1.92 +/- 0.33 for the non-invasive group, and there was no significant difference between the two groups regarding uptake of the agent (p 0.53). Furthermore, it was determined that the invasive and non-invasive adenomas displayed an uptake of Tc-99m TF similar to normal pituitary tissue. Conclusions: Since the pituitary adenoma and normal pituitary tissue gave similar results regarding Tc-99m TF uptake, it was concluded that this agent would not be useful in the diagnosis of pituitary adenoma.