Background: In the treatment of active tuberculosis, therapeutic drug monitoring (TDM) is used to optimize dosing that maximizes therapeutic benefit while minimizing toxicity. In Morocco, TDM is not routinely used, yet low levels of anti-TB drugs can be associated with poorer treatment outcomes.Methods: We retrospectively checked our archives for patients with active TB for whom TDM was performed during 2014. Medical records were reviewed to abstract demographic, clinical, radiographic and microbiological data including time until smear and culture conversion. Then, we looked for cases with delay of TB conversion.Results: In total, 24 patients were identified, for whom TDM was performed, they all had low serum drug levels. Among them, 4 patients showed delayed bacteriological... conversion.Conclusions: Our study cases are showing the benefit of serum dosage in the follow-up of the patients showing a delay of sputum examination conversion, both direct and culture, during their evolutions. TDM is potentially useful for the treatment of active TB, but is currently underused in Morocco.