The electrochemical frequency modulation (EFM) technique has been used to investigate its ability to monitor stress corrosion cracking (SCC) of sensitized stainless steel U-bend specimens in sodium thiosulfate (Na2S2O3) and sodium chloride (NaCl) solutions. Type 304 (UNS S30400) stainless steel was sensitized for different times to vary the SCC susceptibility. With EFM, a potential perturbation composed of two sine waves generates current responses at multiple frequencies. Because of the nonlinear nature of a corroding system, the alternating current (AC) response contains nonlinear components at harmonic and intermodulation frequencies. Analysis of these components provides information about the corrosion behavior of the system under investigation like the uniform corrosion rate. SCC has been investigated by measuring the so-called "causality factors," which are calculated from the ratio of the current components in the AC response. A mathematical model is developed based on the causality factors during SCC. Both theoretical and experimental results show that the causality factors change when the system goes from uniform corrosion to SCC.