Different techniques are presented that measure non-destructively eggshell. The incidence of broken and cracked eggs range from 6% to 8% of all eggs produced. Breaking force strength has proven to be closely related to the proportion of broken eggs but the relationship with non-destructive measurements is not yet clear. Therefore, the relationship of deformation (static stiffness), compression cone hardness and dynamic stiffness with breaking force strength was measured as a non-destructive alternative. Samples of 180 white and brown eggs (n = 360) each from hens at different ages (33, 58 and 71 wks) were used for deformation analysis, acoustic impulse (using an acoustic crack detection device), compression cone hardness and breaking force strength. Calculations from multiple regressions indicated that compression cone hardness and dynamic stiffness have stronger influences on breaking force strength than static stiffness (deformation). It seems to be necessary, to develop other measurements for estimating eggshell quality without destroying the egg shell. Compression cone hardness (CCH), shell deformation, shell breakage strength, shell thickness, static stiffness, dynamic stiffness and shell mass had the best coefficients of correlation. Also it was the best assessment for practical large scale uses, because the age changes the characteristics of egg shell quality from time to time. Intact eggs produced sound signals mainly exhibiting a single dominant peak in the frequency range of 3000-8000 Hz with signal duration of about 20 ms. The cracked eggs showed frequency spectra in relatively wider frequency range of 200010000 Hz and shorter signal duration of about 15 ms. Finally, it was concluded that the influence of the material strength (breakage force) upon total eggshell strength (crack detector) is limited. Calculations from multiple regressions indicated that compression cone firmness and dynamic stiffness have stronger influences on static stiffness than breakage force strength. Structural strength, (CCH) on the other hand plays a more important role upon total shell strength for eggshell stability and relating the structure to its functional properties and textures behind the strength of biomaterials could be used in the attempt of bioengineering new systems, where it would offer an excellent method to understand eggshell solidity to improve eggshell quality and reduce the incidence of cracked eggs. (C) 2009 Elsevier Ltd. All rights reserved.