Interactions of 20-GeV/c negative pions in photographic emulsion have been analyzed in order to compare and test the methods of energy estimation commonly used in high-energy cosmic-ray investigations. The energy of each pion interaction has been determined from the angular distribution of the secondary particles using the median-angle, Castagnoli, $E_{\mathrm{ch}}$, and $E\left(\theta \right)$ methods. The interactions have been divided into various groups according to the number $N_h$ of evaporation prongs and the number $n_s$ of secondary particles. The median-angle, Castagnoli, and $E\left(\theta \right)$ methods all overestimate the energy of the group with $N_h\le 5$ ($n_s\ge 4$) by factors of 1.5, 1.2, and 1.1, respectively. These same methods underestimate the energy of the group with $N_h>5\mathrm{}$ ($n_s\ge 4$) by factors of 1.3, 2.0, and 2.3, respectively. The $E_{\mathrm{ch}}$ method underestimates the energies of the groups with $N_h\le 5$ ($n_s\ge 4$) and $N_h>5\mathrm{}$ ($n_s\ge 4$) by factors of 1.3 and 1.5, respectively. These underestimates by the $E_{\mathrm{ch}}$ method become 0.9 and 1.0 if the general practice of including the effect of neutral secondaries to the $E_{\mathrm{ch}}$ method is adopted. For all the various groupings of $N_h$ and $n_s$ considered, the $E_{\mathrm{ch}}$ method yields the most consistent and uniform results with the smallest standard deviations than any of the other three methods.

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