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L-arginine and its precursor and metabolite, l-citrulline, are two amino acids involved in the production of nitric oxide (NO). As a result, they increase blood flow and have been used to treat male sexual dysfunction. We aimed to evaluate whether a topical gel containing l-arginine and l-citrulline could increase blood flow to the clitoris. Sonography of the clitoris was performed on a healthy 32-year-old volunteer before and after applying the gel externally to the vulva. The ‘‘before’’ scans were obtained using a neutral ultrasound gel (without larginine or l-citrulline). This allowed us to verify that the observations were due to the active ingredients of the gel, and not from massage associated with its application. Control images without gel could not be obtained, since acquisition of ultrasound images requires ultrasound gel in order to reduce acoustic impedance. The scans were obtained with a Philips LumifyTM ultrasound (Koninklijke Philips N.V., Amsterdam, Netherlands) with a L12-4 linear array transducer (4—12 MHz). Clitoral blood flow was assessed qualitatively (color Doppler images), as well as quantitatively (peak systolic velocity, end diastolic velocity, and resistive index of the deep artery of the clitoris). Clitoral blood flow and velocities increased after application of the gel containing l-arginine and l-citrulline at the time points assessed (5 and 15 minutes). Difficulty achieving clitoral stimulation is a major cause of sexual dysfunction. Clinicians can use these findings to counsel patients about using gels to increase clitoral blood flow.