This study compared the longevity of high strength posterior glass ionomer and metal-reinforced glass ionomer using ART in rural settings within an 18-month observation period. A nonblinded parallel design randomized controlled trial was conducted among children who attended dental outreach programs in a rural area of Southern India. Atraumatic Restorative Treatment (ART) was performed in 92 permanent posterior teeth with either high strength posterior glass ionomer or metal-reinforced glass ionomer restorations. The allocation ratio was 1:1. Restorations were evaluated at 1, 6, 12 and 18 months after placement. The success rate of metal-reinforced glass ionomer restorations was 100%, 95.4%, 90.4% and 87.2% as compared to high strength posterior glass ionomer whose success rates were 100%, 93%, 85% and 61.8% at the four follow ups respectively. There was a statistically significant difference between the success rate of the two materials at the end of 18 months with the metal-reinforced glass ionomer restorations having a higher success rate (p=0.015). Conclusions : Although the clinical performance of both materials were largely similar, the metal-reinforced glass ionomer restorations had a higher success rate than the conventional GIC at the end of 18 months of follow-up.