The purpose of this case report is to present success and failure outcomes of seven-year follow-up of resin infiltration treatment (RIT) used for the proximal caries of maxillary premolars. Although resin infiltration can be a good option for micro-invasive treatment, long-term follow-up data are not sufficient, and the outcome of this technique can be affected by factors such as technique sensitivity of procedure, patient's caries risk, and depth of caries progression. Therefore, careful case selection, application, and follow-up are needed.