This study aimed to assess the safety, tolerability, efficacy, and compliance of a risperidone long-acting injection (RLAI) formulation for the maintenance treatment of stabilized bipolar patients. A prospective, open-label trial of RLAI was conducted for 12 months. Stable bipolar patients (n=11) were switched from their existing oral antipsychotic agents to RLAI, and injections were given every 2 weeks. The assessments were performed at baseline and at 6 and 12 months of treatment by using the Young Mania Rating Scale (YMRS), Clinical Global Impressions-Severity of Illness (CGI-S) scale, 17-item Hamilton Rating Scale for Depression (HAM-D), Brief Psychiatric Rating Scale (BPRS), and Extrapyramidal Symptom Rating Scale (ESRS). The satisfaction levels of subjects were evaluated at the end of the study period using a 10-point visual analog scale. Ten patients (90.9%) completed the trial, and no significant changes were seen in the YMRS, HAM-D, and BPRS scores throughout the study. CGI-S and ESRS scores were significantly decreased from the baseline to the post-12-month treatment score. Relapses were not reported by any of the participants. This result indicates that RLAI may be beneficial in the maintenance therapy of stable bipolar patients; however, an adequately powered, randomized, placebo-controlled trial is necessary to draw a definite conclusion about the role of RLAI in the maintenance treatment of bipolar patients.