The structure and morphology of Nylon-12,10 lamellar crystals has been investigated using transmission electron microscopy, selected area electron diffraction, and x-ray diffraction. Additional data have been obtained from uniaxially oriented fibers. The unit cell parameters of two crystalline structures have been determined. They are similar to those usually found in other polyamides (alpha and beta form). Calorimetric (DSC) studies on nylon 12,10 were also carried out. Melting curves indicate that changes in the internal structure occur when scanning speeds less than 80 degrees C min(-1) are used.