Papillary thyroid microcarcinoma (mPTC) is being diagnosed increasingly frequently. Multifocality and nodal involvement are sometimes reported on diagnosis. Management ranges from observation to total thyroidectomy (Tx) followed by radioiodine (RAI) ablation. The role of rhTSH testing in mPTC has not been fully investigated. Torlontano et al. (2006) recently observed that rhTSH-stimulated Tg levels mainly depend on normal tissue remnant. Aim of this study was to further evaluate the role of rhTSH testing in mPTC. From a cohort of 52 subjects with mPTC (52.4±15.8 years, 44 females; average follow-up 4.6 years, range 126 years) 69% underwent total Tx and 39% Tx plus RAI; 24 subjects were also evaluated by standard rhTSH testing. Tg levels were measured from days 0 to 9 and 0.9 mg of rhTSH was given on days 1 and 2. Ablative RAI had been performed in 18 of the 24 subjects. Tg levels were <1 ng/ml after rhTSH administration in 89% of these RAI-treated patients and in 50% of those not treated with RAI. In 1 subject treated with total Tx plus RAI and in 3 treated only with Tx, increased Tg levels after rhTSH were interpreted as a consequence of a remnant of normal thyroid tissue, as revealed by neck sonography, and length of time from diagnosis. In only 1 patent were Tg-stimulated levels 12 months after RAI regarded as probably due to persistence of thyroid disease. In conclusion, our experience shows that undetectable Tg levels can be observed long after Tx, even in 50% of mPTC not ablated with RAI. RAI ablation increases the rate of patients in whom a disease-free condition can be recognized early. RhTSH testing is also useful in non-ablated patients without evidence of disease on neck sonography, in whom undetectable Tg levels may indicate a disease-free condition sooner than clinical follow-up.