Background/Aims: Sclerotherapy with aluminum potassium sulfate and tannic acid (ALTA) has a potent effect on internal hemorrhoids. In this retrospective study, we compared the effects of endoscopic ALTA therapy and standard ALTA therapy. Methods: We investigated patients who underwent treatment for internal hemorrhoids at our institution between 2014 and 2016. They were divided into a standard ALTA group (n=33, treated using proctoscopy) and an endoscopic ALTA group (n=48). We compared the clinical findings between the 2 groups. Results: There were no intergroup differences in background factors. The mean ALTA dose was 21.9±7.2 mL and 17.8±3.4 mL in the standard and endoscopic ALTA groups, respectively (p<0.01). Adverse events occurred in 4 patients (12.1%) from the standard ALTA group and 6 patients (12.5%) from the endoscopic ALTA group. In both groups, the patients reported good satisfaction with the therapeutic effect at 1 month after the procedure. Hemorrhoids recurred in 2 patients (6.3%) from the standard ALTA group and 4 patients (8.3%) from the endoscopic ALTA group. Conclusions: Endoscopic ALTA sclerotherapy is equivalent to standard ALTA therapy in terms of efficacy, adverse events, and recurrence. Therefore, it is a useful non-surgical option for patients with internal hemorrhoids who prefer a less invasive treatment. Clin Endosc 2019;52:581-587