Objective: Resin infiltration is a new microinvasive treatment to arrest the progress of proximal initial caries lesions. This study evaluated the clinical applicability of proximal caries infiltration. Method and Materials: In the study population of 50 children, adolescents, and young adults (mean age, 17.3 ± 6.4 years), 10 dentists at the University of Greifswald, Greifswald, Germany, applied the infiltration material Icon on noncavitated proximal lesions in permanent and primary teeth as described by the manufacturer. The applicability was evaluated using two questionnaires filled out by clinicians and patients assessing the comfort, complexity, time, and difficulties of the application in comparison to a filling. Results: The results showed good patient satisfaction with the procedure. The mean time for infiltration (24.3 ± 7.4 minutes), which included rubber dam application (7.7 ± 4 minutes) and the effort were perceived to be comparable to or even easier than a composite filling by clinicians. In three patients (6%), it was not possible to gain sufficient proximal space for the application of an infiltration. The location of the infiltrated tooth, separation problems, and the routine of clinicians with the infiltration technique had an effect on the duration of the infiltration. A clear learning curve with a reduction of treatment time for subsequent treatments was observed (P .001). Conclusion: Resin infiltration of initial noncavitated proximal lesion showed good clinical applicability for clinicians and very high acceptance by patients. Keywords: caries infiltration, clinical applicability, initial lesions, patient satisfaction, proximal caries