Describes research directed toward developing parametric estimating relationships for the production costs of avionics suites and systems. The research sample comprised 17 combat aircraft and their avionics equipment. Potential explanatory variables were selected based on interviews with manufacturers about factors affecting avionics costs and the appropriateness of the variables for use in planning studies early in system acquisition. Multivariate regression analysis techniques were used to determine the statistical properties of candidate estimating relationships for whole suites and individual systems. The estimating equations derived for suites were generally satisfactory but not always as statistically efficient as desirable. Attempts to derive estimating relationships for avionics systems were much less satisfactory but offer improvements over the simple cost-per-pound metrics often used. The authors conclude that objective means for expressing technology change and its importance for avionics cost estimation remain a concern for future research.