Rice has grown to be the most economically important food crop in numerous countries due to food diversification. The increase in rice productivity has become fundamental in order to meet the world’s current population growth rate. However, as the availability of arable land continues to decline it is crucial to increase crop yield through the development of high yielding varieties. In the present study fifteen advanced breeding lines of rice (FG12-23, FG12-49, FG12-259, G14-10, G15-02, G15-11, FG15-01, FG15-02, G16-102, G16-104, G16-108, G16-112, FG14-43, FG15-35, G13-126) were evaluated in a randomized complete block design with three replicates in the background of commercial varieties GRDB FL 10, GRDB FL 12 and GRDB FL 14 for their yield and yield attributing traits. The trial was conducted at Black Bush Polder, Region 6 during the first and second crop/season of 2018 in Guyana. Mean values for quantitative traits viz. plant height, productive tillers/m2, lodging %, grain yield, panicle length, filled and unfilled grains per panicle, spikelet fertility and 1000 grain weight were compared according to least significant differences (LSD) statistical test. All traits examined showed some degree of significant variability. Line FG12-259 recorded the most tillers/m2 (338) as well as the highest grain yield (7276.6 Kg/ha) over the two seasons. With regards to filled and unfilled grains per panicle, lines G16-108 and G16-104 both recorded 168 filled grains per panicle which was significantly higher than the other tested lines while G16-104 also recorded the most unfilled grains per panicle (45). GRDB 10 was observed to have the highest spikelet fertility (90.7%) while G15-02 attained the lowest (73.5%). Panicle length ranged from 21.67cm in G16-108 to 29.56cm in GRDB 12 while maximum 1000 grain weight was 30.75g (G15-02) and the minimum 22.53g (G16-108). The plant height of the tested lines ranged from semi-dwarf to intermediate averaging 108.7cm. Relatively low incidence of lodging was observed (<12%) as only four of the tested lines G15-11, FG15-01, GRDB 10 and GRDB 12 showed signs of lodging. FG12-259 was recommended for further evaluation in farmers’ fields.