This paper has surveyed the laws restricting the use of hypodermic needles and syringes for injection of illegal drugs. It has reviewed the constitutional basis for these laws and concluded that they are on sound footing. There is a new Federal law regulating needles and syringes in interstate commerce, but it is too early to tell how expansively it will be implemented. A large majority of States have drug paraphernalia laws that govern needles and syringes, and a smaller number have laws that require prescriptions for the sale and possession of needles and syringes. Some local jurisdictions also have laws, but these were not specifically reviewed. Altogether, a breadth of relevant laws govern the manufacture, sale, use or possession, advertisement, and interstate commerce of needles and syringes intended for use with illegal drugs. Any attempt by scientists or public health officials to accurately study the effect of these legal restrictions on the HIV infection rates in differing jurisdictions must comprehensively consider the applicable laws. Likewise, attempts at legislative change must also identify each law that would apply. Prosecutorial discretion has been discussed as it relates to the decision not to prosecute offenses involving the illegal use of needles and syringes. While prosecutorial discretion is most likely to be used by prosecutors in individual cases, it provides a legally sound approach for a prosecutor who decides not to enforce the needle and syringe laws across the board as part of an HIV infection control program. Although this approach has not yet been adopted in this country, a prosecutor's decision not to enforce these laws might allow the establishment of an experimental program, such as one for needle exchange, that could serve as a laboratory for legislative initiatives.