The evolution of techniques has increased the number of diagnosed thyroid papillary microcarcinoma challenging the previous therapeutic guidelines. We have studied all thyroid cancers in our data base (from 1953 to 1994, N = 698). One-hundred and eleven were papillary microcarcinomas (none before 1967): 83 M0N0, 24 M0N+ et 4 M+. One-hundred and eight pathologic slides could be obtained and were checked by one of us (pathologist). The mean follow-up was 8.6 yr [1-28]. Two clinical and pathological features were different between M0N0 and M0N+ (groups: i) the sex-ratio, 12 vs 50% men (M0N0 vs M0N+, p < or = 0.0001), ii) the invasiveness of the tumor, 54/83 vs 20/24 (M0N0 vs M0N+, p = 0.01). All patients received a suppressing treatment by thyroid hormones (except lobectomy). The other treatments were: for 64/83 M0N0 a total thyroidectomy followed by a I131 treatment, for the remaining no I131 (15 partial thyroidectomies and 4 total thyroidectomies). None of the M0N0 patients displayed metastasis or cancer relapse. All patients M0N+ had a total thyroidectomy followed by a I131 treatment. Among the latter, I had a major node evolution, the death was attributed to the cancer at the age of 83 after a 6 yr long evolution. Among the 4 patients considered as metastatic. 1 was poorly differentiated. For the remaining 3, the thyroidal origin of the metastasis was not clear. In summary, the papillary microcarcinomas display a good prognosis if devoid of metastasis. We propose the following guidelines: a total thyroidectomy followed by a I131 treatment and suppressing treatment if clinical nodes, or non-encapsulated tumor or multifocal tumor. For solitary tumors, well encapsulated a lobectomy appears sufficient.