During the last decade, the veterinary anesthetics have gained popularity as recreational drugs. The aim of this study was to document the use of "anestecia de caballo" (xylazine) and its consequences among drug users in Puerto Rico. The study combined a cross-sectional survey with 89 drug users and two focus groups conducted in Mayagüez with frontline drug treatment providers. Drug users were recruited from communities of the San Juan metropolitan area using a variety of ethnographic and outreach strategies. A short questionnaire developed for the study collected information on sociodemographics, xylazine use, and its consequences. The two focus groups were conducted to discuss the details related to xylazine use, its consequences, and utilization awareness. The sample comprised 63 males (70.8%) and 26 females with a mean age of 37.2 years. The mean number of years of drug use was 14.3, with a mean frequency of drug use of 5.9 times daily. More than 65% reported speedball as the principal drug of use. The prevalence of xylazine use was 80.7%. More than 42% of the sample used xylazine in a mixture with speedball. The main route of administration of xylazine was injection but 14% reported the use of xylazine by inhalation. More than 35% of the sample reported skin lesions and 21.1% reported at least one overdose episode. Multiple logistic regression analysis revealed that males (OR = 3.47, CI = 1.10-12.00) and those who reported speedball as their main drug of use (OR = 9.34, CI = 2.51-34.70) were significantly more likely to be xylazine users. Focus groups revealed that drug users claimed to recognize the presence of xylaxine in a mixture of speedball based on its effects, taste, the color of the drug (dark brown), and its odor. In conclusion, the use of xylazine among drug users in Puerto Rico seems to be an emerging trend with potentially serious health consequences.