Objective: The aim of the present study was to evaluate the clinical performance of four denture soft liners up to 12 months. Materials and methods: Thirty-three edentulous patients who experienced difficulties when using hard denture bases because of changes in denture-supporting tissues were accepted for the study and randomly received Molloplast B, GC Reline Soft, Silagum Comfort, or Mollosil Plus relines. Performance of the materials was evaluated using nine criteria at 3, 6, and 12 months: physical integrity, surface detail, adhesion, color, odor, plaque accumulation, resilience, hygiene, and mucosal condition. A four-point categorized scale (1=poor, 2=fair, 3=good, 4=excellent) was used. Unscheduled maintenance events and the presence of fungal colonization were also recorded. Results: The percentage of patients available at 3, 6, and 12 months were 91%, 91%, and 66%. Main reasons for dropouts and discontinuation were fractured dentures and patient dissatisfaction. At 6 months, 96% of the performance scores were good or excellent and the largest changes were observed for physical integrity, surface detail, color, and fungal colonization. Fungal colonization was the most commonly observed problem and was the only reason of failure at 12 months. Conclusions: The clinical performance of all soft liners was slightly impaired over the 12-month observation. Except for cases showing extensive fungal colonization, the observed changes in clinical performance did not necessitate remaking of the dentures. Mollosil Plus showed a performance comparable to that of Molloplast B, and the other materials had slightly lower performance especially in terms of fungal colonization.