Follicular mucinosis can occur as a primary idiopathic disorder or can arise in association with benign or malignant disease, most notably mycosis fungoides. We describe a patient with an aggressive folliculotropic variant of mycosis fungoides that initially presented as follicular mucinosis with alopecia. One month after the diagnosis of follicular mucinosis, a diagnosis of mycosis fungoides was made, and 3 months later inguinal lymph node involvement with mycosis fungoides developed. A skin biopsy specimen demonstrated prominent follicular mucinosis with folliculotropism of atypical cells and intrafollicular Pautrier's microabscesses. As demonstrated in this case, follicular mucinosis can be a presenting sign of rapidly progressive mycosis fungoides. In our review of follicular mucinosis and its association with mycosis fungoides, we found that the folliculotropic variant of mycosis fungoides appears more commonly to have an aggressive course than classic mycosis fungoides. (J Am Acad Dermatol 2000;43:635-40.).