Prepulse inhibition (PPI) is an automatic and preattentive process, whereby a weak stimulus attenuates responding to a sudden and intense startle stimulus. PPI is a measure of sensorimotor filtering, which is conceptualized as a mechanism that facilitates processing of an initial stimulus and is protective from interruption by a later response. Impaired PPI has been found in (a) healthy women during the luteal phase of the menstrual cycle, and (b) individuals with types of psychopathology characterized by difficulty suppressing and filtering sensory, motor, or cognitive information. In the current study, 47 trauma‐exposed women with or without posttraumatic stress disorder (PTSD) completed a PPI session during two different phases of the menstrual cycle: the early follicular phase, when estradiol and progesterone are both low, and the midluteal phase, when estradiol and progesterone are both high. Startle stimuli were 100 dB white noise bursts presented for 50 ms, and prepulses were 70 dB white noise bursts presented for 20 ms that preceded the startle stimuli by 120 ms. Women with PTSD showed deficits in PPI relative to the healthy trauma‐exposed participants. Menstrual phase had no effect on PPI. These results provide empirical support for individuals with PTSD having difficulty with sensorimotor filtering. The potential utility of PPI as a Research Domain Criteria (RDoC) phenotype is discussed.