Synthetic polyamide textile materials made from drawn filaments of a polycondensate of e -aminocaproic acid are crimped and shrunk by treating them with a solution of formaldehyde in an aliphatic alcohol containing an acid catalyst at a temperature of 50 DEG -80 DEG C. The drawn polyamide filaments are those which have been drawn to at least 250% of their original length. The formaldehyde may be in the form of para-formaldehyde and the alcohol is preferably one having 1-6 carbon atoms. Specified catalysts are oxalic, maleic, fumaric, mono-, di- and tri-chloroacetic, p-toluenesulphonic and phosphoric acids, ammonium bromide and calcium chloride. The treatment may be effected at 60 DEG -80 DEG C. for 5-10 minutes. The textile materials may be in the form of yarns, filaments, threads or woven, non-woven or knitted fabrics.