Objectives: To assess whether public health nurses adhered to Dutch guidelines for tuberculosis contact investigations and to explore which factors influenced the process of identifying contacts, prioritizing contacts for testing and scaling up a contact investigation. Methods: A multiple-case study (2010-2012) compared the contact investigation guidelines as recommended with their use in practice. We interviewed twice 14 public health nurses of seven Public Health Services while they conducted a contact investigation. Results: We found more individuals to be identified as contacts than recommended, owing to a desire to gain insight into the infectiousness of the index case and prevent anxiety among potential contacts. Because some public health nurses did not believe the recommendations for prioritizing contacts fully encompassed daily practice, they preferred their own regular routine. In scaling up a contact investigation, they hardly applied the stone-in-the-pond principle. They neither regularly compared the infection prevalence in the contact investigation with the background prevalence in the community, especially not in immigrant populations. Nonadherence was related to ambiguity of the recommendations and a tendency to act from an individual health-care position rather than a population health perspective. Conclusions: The adherence to the contact investigation guidelines was limited, restraining the effectiveness, efficiency and uniformity of tuberculosis control. Adherence could be optimized by specifying guideline recommendations, actively involving the TB workforce, and training public health nurses. © 2012 Mulder et al.