Purpose: To evaluate the medium-term effectiveness of 6.5 mm-long flapless-placed single implants immediately or early loaded at 6 weeks. Materials and methods: Thirty patients received two single NanoTite external hex Biomet 3i implants each, which were then randomly allocated to be immediately or early loaded according to a splitmouth design. Implants had to be inserted with a minimum torque of >40 Ncm. Provisional crowns were put in slight occlusal contact and replaced by definitive crowns 3 months after loading. Patients were followed for 4 years after loading. Outcome measures were implant failures, biological and biomechanical complications, peri-implant marginal bone level changes, and patient preference. Results: Twenty-nine implants were immediately loaded and 31 early loaded. Four years after loading, no drop-outs occurred. One implant failed in each group within 2 months after loading. Seven patients experienced complications at immediately loaded implants and 6 at early loaded implants. There were no statistically significant differences between groups for implant losses, complications, mean marginal bone level changes and patient preference. Conclusions: Flapless-placed 6.5 mm-long single implants can be immediately loaded and remain successful up to 4 years after loading. Even longer follow-ups are still needed to evaluate the longterm prognosis of short implants. Keywords: dental implants, early loading, flapless, immediate loading, short implants