Periodontal probing is commonly used for assessing both the status of gingival health and the connective tissue attachment level around teeth. The role of probing around endosseous implants still remains unclear. The purpose of this study was to determine the histological level of probe penetration in healthy and inflamed mucosal tissues around implants. Five beagle dogs were used and a total of 30 one-stage, Titanium Plasma Spary (TPS)-coated implants of the ITI type were placed in the mandibles. After the healing period with meticulous oral hygiene, the dogs were divided into 3 groups: 1) clinical healthy mucosal tissues; 2) experimental mucositis (3 dogs); and 3) experimental ligature-induced peri-implantitis (2 dogs). Four months after implant placement, respectively 6 months in the third group, 60 probes were placed with a standardized force of 0.2 N and fixed at the mesial and distal aspects of the implants. Probing depth, clinical attachment level (CAL), Plaque Index (PlI) and Gingival Index (GI) were assessed throughout the study. Tissue sections were obtained for histometrical analysis. In the healthy group, the mean PII was 0.47, the GI 0.06 and the clinical probing depth (CPD) 2.12 mm. In the mucositis group the PlI was 1.61, the GI 1.61 and the CPD 1.87 mm. In the peri-implantitis group the PlI was 1.96, the GI 2.05 and the CPD 3.73 mm. The histologic results show that the probes were able to identify the connective tissue adhesion level in the healthy group with a mean error of -0.05 mm (mean histologic probing depth (HPD): 1.75 mm) and, in the mucositis group, with -0.02 mm (mean HPD: 1.62 mm). Probe penetration increased with the degree of inflammation and in the peri-implantitis group the probe exceeded the connective tissue level by a mean 0.52 mm (mean HPD: 3.8 mm). Therefore, probing around implants represents a good technique for assessing the status of peri-implant mucosal health or disease.