For long-term operation of main oil and gas pipeline steels the technique of deterring the
critical crack growth resistance of pipeline steels by investigation using experimentally obtained
diagram of "force-deflection" samples destruction was suggested. The sizes of through critical
cracks have been calculated and the initial sizes and the shape of crack-like defects for the
investigated main gas and oil pipelines were evaluated. The obtained data can serve as a basis for
the interpreting detected crack-like defects during technical diagnostic
