Early stages of connective tissue reattachment to surgically denuded cementum and root dentin following citric acid application were studied in fenestration wounds. Block specimens were obtained after seven, 14, and 21 days. Continuity between newly deposited collagen fibrils in the granulation tissue and unmasked dental matrix collagen had been established within seven days by interdigitation of fibrils in an up to 0.5 micron-wide zone at the cementum or dentin surface. Splicing of collagen at the fibrillar level by direct attachment to the severed end of matrix fibrils or by juxtapositioning of new and old fibrils was seen in rare instances only. At 14 and 21 days, distinct bundles of collagen fibrils inserted deeply into the orifice of dentinal tubules. Arrested and reversed surface resorption was encountered at all time points. At these sites as well, new collagen fibrils interdigitated with denuded matrix collagen, while some resorbed surfaces were characterized by absence of collagen continuity. The results lend continued support to the concept of reattachment based on interdigitation of collagen fibrils. However, since attachment is established even in the absence of this feature, a significant role for specific attachment substances not shown can also be postulated.