Since the original descriptions of follicular mucinosis, accumulating experience shows that patient age, distribution of lesions, and duration or extent of disease do not reliably distinguish benign primary follicular mucinosis from secondary follicular mucinosis, associated with cutaneous lymphoma. More recently, it has been suggested that individuals with follicular mucinosis demonstrating a clonal T-cell receptor gene rearrangement may be at higher risk for the development of lymphoma. Long-term follow-up of 7 patients younger than 40 years with primary follicular mucinosis are reported. In all cases, there was no clinical or histologic evidence of associated dermatoses or lymphoma at the time of diagnosis. Five of the patients have clonal T-cell gene rearrangement as determined by Southern blot analysis. Clinically, at the time of diagnosis, lesions of primary follicular mucinosis ranged from papules confined to the face to widespread cutaneous plaques. After a mean follow-up of 10 years (range, 5-23 years) from the onset of disease, the majority of patients continue to have cutaneous manifestations of follicular mucinosis despite various treatments. There is no evidence of progression to cutaneous T-cell lymphoma in any patient despite the presence of a clonal T-cell receptor gene rearrangement. Continued prolonged follow-up of patients with clonal primary follicular mucinosis is necessary to determine the significance of infiltrates harboring a T-cell receptor gene rearrangement. However, in our experience with this group of selected patients, primary follicular mucinosis has been a clonal disorder with limited or "benign" cutaneous manifestations.