Calorimetric (DSC) and Small Angle X-ray Scattering analyses were used to study the structure and morphological properties of nylon 4,6 single crystals grown in a 1,4-butanediol solution at varied crystallizati temperatures. DSC analysis was used to determine an obtained crystallinity range of 40-50%, slightly higher than the reported range for nylon 6,6 single crystals. Small Angle X-ray Scattering was used to measure lamellar thickness (characterized by a horizontal plateau at crystallization temperatures [T_c] below 130℃, followed by monotonic thickness increases for T_c beyond 130℃). Samples were annealed to remove residual solvents from within the crystals; thermal properties of the crystals were measured to verify the effect of annealing on crystal perfection. DSC melting peaks obtained with scanning rates of less than 80K/min, indicated that changes in the internal morphology of 4,6 crystals occur during heating. The melting temperatures (T_m) of single crystals produced at different crystallization temperatures were plotted against their reciprocal thicknesses to calculate a thermodynamic melting point of 319℃ for an infinitely extended crystal (T_m). Likewise, measured heat fusion values (ΔH_m) were plotted against reciprocal thicknesses to establish a heat fusion value of 270 J/g infinite crystal thickness (ΔH_o). Applying these values to the Hoffman-Weeks equation yielded a fold surface energy value (σ_e) of 65 erg/㎠.