Aim: Aim of the investigation was a comparison of the clinical, microbiological and immunological situation of the peri-implant tissues in edentulous patients wearing long-standing lower complete dentures retained by either Dolder bar or ball attachments. Methods: During a regular recall visit (mean time since implant insertion: 7 years) the following findings were examined in 10 individuals with good oral hygiene, matched for age and gender (mean age 71 years) and wearing either a Dolder bar or ball retained complete mandibular denture: sulcular fluid flow rate (with Periotron device), plaque- and bleeding scores, pocket probing depth, implant stability (Periotest device), subgingival bacterial plaque samples (PCR diagnostics, Hain MicroIdent), and sulcular concentrations of the mediators interleukin 1 beta and prostaglandin E2 (total concentration per site and per µl sulcular fluid in 120 seconds). Results: No statistically significant differences could be observed between the two groups of patients with Dolder bar and ball retained implant restorations with regard to their peri-implant clinical, microbiological, and immunological findings. Conclusions: Having in mind the relatively small number of patients included in the investigation the microbiological and immunological findings confirm the nearly identical pattern of influence , for either retentive concept, on the peri-implant soft tissue observed clinically even after a long period of function. Keywords: Implant supported complete denture, Dolder bar, ball attachment, microbiology, sulcular fluid, interleukin 1 beta, prostaglandin E2