The study objective was to compare the prevalence of herbal product use between El Paso, Texas, and Ciudad Juárez, Chihuahua, the largest U.S./México border population. 500 households on each side of the border were randomly selected following a strict procedure for household and participant selection. 1001 adult residents of selected households participated. Trained bi-lingual interviewers conducted semistructured interviews using a bi-lingual questionnaire. A chi-square test was used to compare populations when considering discrete variables and a t test was used for continuous variables. There was no significant difference in the overall prevalence of herbal product (HP) use between the El Paso (68%) and Ciudad Juárez samples (65%). El Paso residents used a greater number of HPs compared to Ciudad Juárez residents (P = 0.001). The most common HPs used in El Paso were chamomile, aloe vera, garlic, peppermint and lime. In Ciudad Juárez, they were chamomile, eucalyptus, garlic, linden tree flower and peppermint. In addition, intra-city variation in the use of HPs was observed. On both sides of the border, relatives were the most common source of advice regarding HP use, and most HPs were reportedly used in raw form. While participants in both groups believed that the HPs were effective and safe, a large number of HPs that could potentially be responsible for drug interactions, and side effects were identified. Very low disclosure rates to physicians were reported (33% in El Paso and 14% in Ciudad Juárez). A high prevalence of HP use was documented on both sides of the U.S./México border. Some significant variations in HP use were also identified. The possibilities of HP-related problems combined with low disclosure rates are of significant concern.