In order to prevent long-term immunity-related complications after lung transplantation, close monitoring of immunosuppressant levels using therapeutic drug monitoring (TDM) is paramount. Novel electronic nose (eNose) technology may be a non-invasive alternative to the current invasive procedures for TDM. We investigated the diagnostic and categorization capacity of eNose breathprints for Tacrolimus trough blood plasma levels (TAC trough) in lung transplant recipients (LTRs). We performed eNose measurements in stable LTR attending the outpatient clinic. We evaluated (1) the correlation between eNose measurements and TAC trough, (2) the diagnostic capacity of eNose technology for TAC trough, and (3) the accuracy of eNose technology for categorization of TAC trough into three clinically relevant categories (low: <7 µg ml −1, medium: 7-10 µg ml −1, and high: >10 µg ml −1 ). A total of 186 measurements from 86 LTR were included. There was a weak but statistically significant correlation (r = 0.21, p = 0.004) between the eNose measurements and TAC trough. The root mean squared error of prediction for the diagnostic capacity was 3.186 in the training and 3.131 in the validation set. The accuracy of categorization ranged between 45%-63% for the training set and 52%-69% in the validation set. There is a weak correlation between eNose breathprints and TAC trough in LTR. However, the diagnostic as well as categorization capacity for TAC trough using eNose breathprints is too inaccurate to be applicable in TDM. @en