Purpose: To compare the effectiveness of immediate post-extractive single implants with delayed implants placed in preserved sockets after 4 months of healing. Implants that achieved an insertion torque of at least 35 Ncm were immediately non-occlusally loaded. Materials and methods: Just after tooth extraction and in the presence of a loss of the buccal plate bone less than 4 mm, compared to the palatal wall, 106 patients requiring a single immediate postextractive implant in the maxilla from second premolar to second premolar were randomly allocated to immediate implant placement (immediate group; 54 patients) or to socket preservation using anorganic bovine bone covered by a resorbable collagen barrier (delayed group; 52 patients) according to a parallel group design at three different centres. Bone-to-implant gaps were to be filled with anorganic bovine bone, however this was not done in 17 patients (corresponding to 40% of those who should have been grafted). Four months after socket preservation, delayed implants were placed. Implants placed with an insertion torque >35 Ncm were immediately loaded with non-occluding provisional single crowns, replaced, after 4 months, by definitive crowns. Outcome measures were implant failures, complications, aesthetics assessed using the pink esthetic score (PES), and patient satisfaction, recorded by blinded assessors. All patients were followed up to 4 months after loading. Results: Nineteen (35%) implants were not immediately loaded in the immediate group versus 39 (75%) implants in the delayed placement group because an insertion torque >35 Ncm could not be obtained. No patient dropped out. Two implants failed in the immediate group (4%) versus none in the delayed group. More minor complications occurred in the immediate group (8) than the in the delayed group (1) and this was statistically significant (P = 0.032). At delivery of definitive crowns, 4 months after loading, aesthetics were scored as 12.8 and 12.6 in the immediate and delayed groups, respectively. There was no statistically significant difference (P = 0.5). Patients of both groups were equally satisfied. Conclusions: There were more complications at immediate post-extractive implants when compared to delayed implants. The aesthetic outcome appears to be similar for both groups and it seems more difficult to obtain a high insertion torque in sockets preserved with anorganic bovine bone. Schlagwörter: delayed, immediate, post-extractive implants