Sebaceous filaments are cylindrical tubes of whitish-yellowish color, which can be expressed from areas of the face rich in sebaceous follicles by pinching the skin or by the cyanoacrylat-technique. Sebaceous filaments are most commonly found in the centrofacial areas and the alae nasae in postpuberal individuals with large facial pores and seborrhea. Sebaceous filaments are composed of a skeleton of 10-30 horny cell layers which enclose a mixture of bacteria, sebaceous lipid, corneocyte fragments and one hair. Following the expression of the filament the follicle refills within 30 days. The various portions of sebaceous follicles (acro- and infrainfundibulum) and the follicular contents are presented at the light microscopial and ultrastructural level. Follicles containing sebaceous filaments have a conspicuous granular layer and no acanthosis. Sebaceous filaments should be differentiated from a microcomedo and trichostasis spinolosa. They are a common morphological variant of sebaceous follicles.