Chain-folded lamellar crystals of nylon 12 14 have been grown from a dilute 1,4-butanediol solution with the "self-seeding" technique. The morphology and structure of nylon 12 14 lamellar crystals were studied by both transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD). Two kinds of electron diffraction patterns were detected when different areas were selected for diffraction, which indicates that the alpha crystal phase and the beta crystal phase coexist for nylon 12 14 under the present crystallization conditions. The WAXD diffractograms of the crystal mats confirm the results obtained from electron diffraction (ED). In addition, the changes of the crystal structure as a function of temperature for melt-crystallized and dilute solution-crystallized nylon 12 14 were monitored by variable-temperature WAXD and variable-temperature infrared spectroscopy (IR). It was found that the melt-crystallized sample undergoes a Brill transformation at 80degreesC-90degreesC, but no Brill temperature can be observed for the dilute solution-crystallized nylon 12 14.