Drawing from 12 in-depth interviews and two focus groups with prosecutors, attorneys, victim advocates, social service providers, and police in an urban Midwestern city, challenges to identifying and prosecuting sex trafficking cases are examined. Challenges to identification included trafficking techniques such as coercion, online solicitation, hidden venues, and interstate movement, as well as issues with police reporting and investigation. Challenges to prosecution involved police reporting errors and evidentiary requirements, the statute of limitations, overlapping jurisdictions, and issues with victim testimony. The aim in highlighting such obstacles is to emphasize the dynamics that may contribute to lowered numbers of identified and prosecuted cases, and consequent underestimation of sex trafficking prevalence. Implications for policy and practice are drawn from these findings.