A self-retaining suture comprises a composite filament. The filament has retainers on the surface such that the filament can engage and retain tissue without knots. The filament comprises at least two materials having different properties. A surface material of the filament has properties which enhance the formation, elevation and/or deployment of the retainers. A core material of the filament has properties which enhance the tensile strength of the filament. The surgical filament is thin and flexible and may be used for suturing. Methods for manufacturing the filament and retainers are also described.