summaryThe aim of this study was to observe the tissue responses to a number of membrane materials processed for use in guided tissue regeneration at different time periods. Non‐degradable Gore‐Tex° PTFE membrane and degradable polylactic acid (PLA) membranes were placed transcutaneously in surgical incisions made in the dorsum of rats. The tissue responses to these materials were observed histologically at 3 days, 1 week and 4 weeks after placement. A wide variation in the tissue responses to both materials was evident at each time period. These variations could not be attributed to different rates of healing over time, but rather to more complex factors. These factors may include differences in host responses between different animals, local factors pertaining to specific site variations, physical characteristics of the materials like surface texture, and contamination from the wound surface. Neither membrane material was found to be totally satisfactory. The PLA membranes were well tolerated by the tissues but they were unevenly absorbed within 2 weeks of placement. The Gore‐Tex PTFE membranes, however, were associated with prolonged acute inflammatory infiltrate throughout the duration of the study, indicating that they were less well tolerated by the tissues than the PLA materials. As the healing characteristics of tissues are complex and highly variable, and as neither the non‐degradable PTFE or degradable PLA membranes demonstrated ideal tissue responses, it is concluded that variations in clinical responses to these materials used in regeneration techniques must be ant