CONTEXT: Suicidal ideation in depressed patients is a serious and emergent condition that requires urgent intervention. Intravenous ketamine, an N-methyl-D-aspartate (NMDA) antagonist, has shown rapid antidepressant effects, making it a potentially attractive candidate for depressed patients with suicidal risk. AIMS: In India few studies have corroborated such findings; the present study aimed to assess the effectiveness and sustainability of antisuicidal effects of ketamine in subjects with resistant depression. SETTINGS AND DESIGN: Single-center, prospective, 4 weeks, open-label, single-arm pilot study. MATERIALS AND METHODS: Twenty-seven subjects with DSM-IV major depression (treatment resistant) were recruited. The subjects were assessed on Scale for Suicidal Ideation (SSI), 17-item Hamilton Depression Rating Scale (HDRS). After a 2-week drug-free period, subjects were given a single intravenous infusion of ketamine hydrochloride (0.5 mg/kg) and were rated at baseline and at 40, 80, 120, and 230 minutes and 1 and 2 days postinfusion. RESULTS: The ketamine infusion was effective in reducing the SSI and HDRS scores, the change remained significant from minute 40 to 230 at each time point. CONCLUSIONS: The real strength of this study rests in documenting the rapid albeit short-lasting effect of ketamine on suicidal ideation in depressed patients.