Purpose: To evaluate short-term follow-up of nonpalpable probably benign lesions in a 2-year mammographic screening., Materials and Methods: Of 13,790 women aged 45-65 years who underwent first-round screening, 795 (5.8%) underwent short-term mammographic follow-up (every 6 months for 2 years) of nonpalpable probably benign lesions (eg, masses, focal asymmetric densities, and calcifications) previously assessed at an additional imaging evaluation, including ultrasonography. When no changes were found at short-term mammographic follow-up, women were assigned to the 2-year screening interval. Needle localization and surgical biopsy were performed when the lesion progressed (was enlarged or had an increased number or size of calcifications or modification of their initial characteristics). The effectiveness of this approach was evaluated with statistical analysis., Results: Of 795 lesions, 788 (99%) remained stable, and seven (1%) had changes prompting surgical biopsy. Two cancers (0.3%), one microinvasive intraductal carcinoma and one 7-mm invasive ductal carcinoma without positive nodes, were found. Four of the five benign histologic results were probably benign calcifications with progression at short-term follow-up. The sensitivity, specificity, accuracy, and positive and negative predictive values were 100%, 99%, 99%, 29%, and 100%, respectively., Conclusion: The benign nature of most nonpalpable probably benign lesions can be typified with short-term mammographic follow-up. This approach permitted identification of a few low-stage carcinomas, but progression in the probably benign calcifications was usually unrelated to malignancy.