The following consensus report is based on four background reviews. The frequency of maintenance visits is based on patient risk indicators, homecare compliance and prosthetic design. Generally, a 6-month visit interval or shorter is preferred. At these visits, peri-implant probing, assessment of bleeding on probing and, if warranted, a radiographic examination is performed. Diagnosis of peri-implant mucositis requires: (i) bleeding or suppuration on gentle probing with or without increased probing depth compared with previous examinations; and (ii) no bone loss beyond crestal bone level changes resulting from initial bone remodelling. Diagnosis of peri-implantitis requires: (i) bleeding and/or suppuration on gentle probing; (ii) an increased probing depth compared with previous examinations; and (iii) bone loss beyond crestal bone level changes resulting from initial bone remodelling. If diagnosis of disease is established, the inflammation should be resolved. Non-surgical therapy is always the first choice. Access and motivation for optimal oral hygiene are key. The patient should have a course of mechanical therapy and, if a smoker, be encouraged not to smoke. Non-surgical mechanical therapy and oral hygiene reinforcement are useful in treating peri-implant mucositis. Power-driven subgingival air-polishing devices, Er: YAG lasers, metal curettes or ultrasonic curettes with or without plastic sleeves can be used to treat peri-implantitis. Such treatment usually provides clinical improvements such as reduced bleeding tendency, and in some cases a pocket-depth reduction of ≤ 1 mm. In advanced cases, however, complete resolution of the disease is unlikely. © 2019 FDI World Dental Federation. Published by John Wiley & Sons Ltd.