The morphology of solution-cast, solution-grown and melt grown crystals of poly(ether nitrile) (PEN) was studied using mainly transmission electron microscopy. Fibrous, lamellar crystals (F crystals) develop during casting from solution followed by heat treatment, and via crystallization from solution and the melt. Electron diffraction studies indicate that PEN crystals grow rapidly along the a* axis, along which the cyano groups are aligned. It can be suggested that an interaction between cyano groups and phenyl rings along the a* axis should favour nucleation on the (200) growth front. F crystals coalesce to form wide lamellar crystals (L crystals) during heat treatment at temperatures above 250 degrees C. PEN formed spherulites with positive birefringence from solution and the melt : the radial growth direction of the spherulites corresponds to the a* axis. In view of the orientation of the cyano groups in the unit cell, it can be suggested that the refractive index along the radial direction is larger than that in the tangential direction. Stacked lamellar structures are formed from the melt under shear; the a* axis is parallel to the transverse direction and the b axis is parallel to the thickness direction. It seems reasonable to assume that preferential nucleation at the be plane occurs on the substrate during oriented crystallization.