In the present work on boiling, local heat transfer coefficient in a uniformly spaced transverse grooved horizontal channel having groove pitch p = 11 mm, groove height e = 1 mm with R - 123 were investigated. An 11.9 mm diameter tube with a heated length of 1000 mm was employed for the test section. The heat transfer coefficient distribution is found out with the mass flux in the range of 181 - 951 kg/ m²s and heat flux of 10 - 155 kW/m². A comparison is also made between the grooved test section and the plain pipe. There is an increase in the heat transfer coefficient in the grooved tube compared with the plain tube at the same heat flux and mass flux conditions. The heat transfer coefficient increases with mass flux at the same heat flux. Similarly, at a given mass flux, heat transfer coefficient increases with a rise in heat flux with grooves in a horizontal tube.