Effects caused by weak nonlinearities of operational transconductance amplifiers (OTAs) on the performance of continuous-time OTA-capacitor (OTA-C) filters are investigated. Nonlinear phenomena, such as compression/expansion and desensitization, are examined and the resulting distortion of the transfer function shape of high-order OTA-C filters with sinusoidal inputs is discussed. The Volterra series method is used to represent filters by their nonlinear transfer function for computer analysis and simulation. Using this approach, distortion and interference criteria are established for predicting analytically the onset of nonlinear behavior in the frequency responses of OTA-C filters. Finally, representative calculation results are presented and verified via SPICE simulations.