Abstract: OBJECTIVE To estimate the target trough concentration in patients with complicated skin and soft tissue infections treated with linezolid and to investigate the predict value of the target trough concentration between clinical efficacy and thrombocytopenia. METHODS In this retrospective, single-center, observational cohort study, 53 hospitalized patients with complicated skin and soft tissue infections who were treated with linezolid due to bacteriologically documented or presumptive Gram-positive infections were extracted. The data were analyzed by t-test, Chi-aquare test (univariate analysis) and Logistic regression analysis(multivariate analysis) using SPSS 22.0 software, the related factors of clinical efficacy and thrombocytopenia were compared. Receiver operating characteristic(ROC) curve was drawn in order to find the best cut-off value to predict clinical feature. RESULTS A significant difference in the first trough concentration of linezolid was observed between the response and non-response groups, and between the thrombocytopenia and non-thrombocytopenia groups. Multiple logistic regression analyses identified the first trough concentration as the only independent variable associated with clinical efficacy and thrombocytopenia of linezolid. The areas under the ROC curves were 0.75 and 0.76 for clinical efficacy and thrombocytopenia, respectively. The cut-off values of the first trough concentration were 6.7 μg·mL^-1 for clinical efficacy (sensitivity 97%, specificity 67%) and 7.5 μg·mL^-1 for thrombocytopenia (sensitivity 77%, specificity 68%). CONCLUSION These results suggest a relationship of trough linezolid concentration with clinical efficacy and incidence of thrombocytopenia. Serum concentration monitoring is required to achieve best outcomes and the goal of individualized treatment of linezolid.