The present invention relates to halogen-free flame retardant compositions essentially comprising polyamide polymers (preferred is polyamide 6), at least a hypophosporous acid metallic salt (preferred is aluminum hypophosphite), at least a nitrogen based flame retardant agent (preferably selected among melamine condensation products such as melam, melem, melon or their mixtures, and melamine cyanurate), at least an organic polyhydric compound and optionally further conventional components. Such compositions are highly flame retardant.