A preliminary version of a new computer program has been developed for calculating crack propagation in cyclically loaded structures. The new program, titled NASA/FLAGRO, has numerous enhanced features over previous programs used for safe life analysis on space systems. The essential features of the new program consist of modular design, promptive input using a cathode ray tube terminal, improved crack growth rate analytical methods, many new crack case solutions, and incorporation of user-defined files for material properties and fatigue spectrums. Also, five options made available in the program are to compute (1) safe life of a part with a preexisting crack, (2) critical crack size for a specified stress level, (3) stress-intensity factor numerical values for making comparisons or checks of solutions, (4) least-squares fit of growth rate equations to crack growth rate data, and (5) to convert a versus N data to ΔK versus da/dN.