Police concern about loud car stereos stems both from the frequency of citizen complaints and the inability of offenders to hear emergency signals and other drivers' horns while driving. This guide, however, focuses on the annoyance aspect of loud car stereos rather than the safety aspect, primarily because there is not much published research and practice related to the latter issue. Understanding the factors that contribute to the problem helps in the framing of local analysis questions, in determining appropriate effectiveness measures, in recognizing key intervention points, and in selecting appropriate responses. The guide advises that amplified car stereos emit a high volume of low-frequency sound through the systems' woofer speakers. Such sounds are usually more annoying than high-frequency noise at similar volume. In addition to being heard, the low-frequency sound waves can often be felt as they cause glass and ceramics to rattle. In addition to the annoyance, overexposure to noise can have a number of negative health and behavioral effects. This guide provides some questions that local police agencies should pose in analyzing the local problem of loud car stereos. The questions pertain to the prevalence and frequency of complaints, the characteristics of complainants and their complaints, offender characteristics and attitudes, locations/times, and current responses. The guide also lists potentially useful measures for determining the effectiveness of responses to the problem of loud car stereos. A section on responses to the problem reviews the effectiveness of the enforcement of noise laws, warnings and education, and a response with limited effectiveness. The latter refers to the enforcement of laws that require police to make subjective judgments about noise. 21 notes, 17 references, and an appended summary of responses to loud car stereos