Factors affecting the soundness of shell eggs are of primary concern to egg processors due to substantial financial losses from cracked and leaker eggs. Ultrastructural analyses were used to examine the palisade layer width and mammillary knob layer thickness of sound, cracked, and leaker eggshells. Subjective observations were also made. There was no significant difference (P > 0.05) in the width of the palisade layer or the mammillary knob layer among sound, cracked, and leaker eggshells. The eggshell strengths of sound, cracked, and leaker eggs were evaluated using puncture force and shell thickness measurements. Sound eggshells were found to have a significantly (P 0.05). Regression and correlation analyses indicated a significant correlation (P 0.05). The correlation coefficient between puncture force and shell thickness was significant (P < 0.01; r = 0.56), indicating a possible relationship.