Chain-folded lamellar crystals of the ten even-even nylons: 6 6, 8 6, 8 8, 10 6, 10 8, 10 10, 12 6, 12 8, 12 10, and 12 12 have been grown from solution and their morphologies and structures studied using transmission electron microscopy, both imaging and diffraction. Sedimented mats were examined using X-ray diffraction. The solution-grown crystals are lath-shaped lamellae and diffraction from these crystals, at room temperature, reveals that three crystalline forms are present in differing ratios. The crystals are composed of chain-folded, hydrogen-bonded sheets, the linear hydrogen bonds within which generate a progressive shear of the chains (p-sheets). The sheets are found to stack in two different ways. Some p-sheets stack with a progressive shear, to form the "alpha(p) structure"; others sheets stack with an alternate stagger, to form the "beta(p) structure". Both the alpha(p) and beta(p) structures give two strong diffraction signals at spacings of 0.44 nm and 0.37 nm; these signals represent a projected intrasheet interchain distance (actual value 0.48 nm) and the intersheet spacing, respectively. Preparations of nylons 6 6, 8 6, 8 8, 12 6, and 12 8 consisted almost entirely of alpha(p)-structure material, with only a trace of beta(p)-structure material being present. In contrast, nylons 10 6, 10 8, 10 10, 12 10, and 12 12 contained substantial quantities of both alpha(p)- and beta(p)-structure material, with alpha(p)-structure material always being in the majority. Preparations of nylons 10 8, 12 10, and 12 12 also showed an additional diffraction signal at 0.42 nm; this signal is characteristic of the pseudohexagonal (high temperature) structure. The melting temperature of solution-grown lamellae of these even-even nylons decreases with decreasing linear amide density. On heating, the strong diffraction signals (0.44 nm and 0.37 nm) gradually moved together and merge at the Brill temperature to form a single diffraction signal (0.42 nm), characteristic of the pseudohexagonal structure. This single diffraction signal remained until melting. For nylons 6 6, 8 6, 8 8, 10 6, and 12 6, the Brill temperatures were substantially below the respective melting temperatures and the single 0.42 nm diffraction signal was stable over temperature ranges of 14 degrees C to 56 degrees C, depending on the nylon. Conversely, nylons 10 8, 10 10, 12 8, 12 10, and 12 12 had coincident melting and extrapolated Brill temperatures.