Abstract: The present invention relates to a filament for 3D printing, comprising (A) at least one semicrystalline polyamide, (B) at least one amorphous polyamide (C) at least one flame retardant of formula (I), wherein R1 and R2 are independently of each other a linear or branched C1-C8alkyl group, or an optionally substituted aryl group, M represents is an alkali metal ion, an alkaline earth metal ion, an aluminum ion, a zinc ion, an iron ion or a boron ion; m represents 1, 2 or 3; and n represents 1, 2 or 3, a process for the preparation of the filament and its use in a process for preparation of a three-dimensional object, by a fused filament fabrication process.