Two-component mixed acrylic composite fibres and yarns with a natural crimp, suitable for carding, stretch breaking and converting said fibers consisting of a mixture of monolaminar, bilaminar and multilaminar strands and made of two polymers A and B, polymer A comprising at least 83% by weight of acrylonitrile, 4 to 15% by weight of a non-ionisable plasticising comonomer, and up to 2% by weight of an acid comonomer which is copolymerisable with acrylonitrile, and polymer B comprising at least 94% by weight of acrylonitrile, 0 to 4% by weight of a non-ionisable plasticising comonomer and up to 2% by weight of an acid comonomer which is copolymerisable with acrylonitrile, the difference in the proportion of plasticising comonomer in the polymers A and B being between 4 and 15% by weight and the total number of milliequivalents of acid in the two polymers being at least 50 per kg of polymer, the said composite fibres and yarns possessing a three-dimensional crimp, the direction of which depends on the heat and/or mechanical treatments to which the composite fibres or yarns have been subjected, polymer B being located on the inside of the helix formed by strands which have been subjected, without tension, to a temperature below about 110.degree. C. and at least equal to ambient temperatures (crimp C 1), and being located on the outside of the helix formed by strands which have been subjected to tension and/or heat treatment at a temperature above about 110.degree. C. (crimp C 2), the contraction and frequency of the two types of crimp varying from one strand to the next and along the length of one strand.