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The Mossoro-Assu-Barauna district, Rio Grande do Norte State (RN), is recognized by the intense production of horticulture, mainly muskmelon for export. However, this region is often devastated by intense droughts. Thus, the muskmelon production is predominantly under irrigated condition and, due to constant threat of water resources collapse on the region, a rigorous irrigation water management in the region is needed. The main objective of this article was to analyze the seasonal pattern of energy balance partitioning and evapotranspiration on irrigated muskmelon crop on the region around Mossoro-RN. The study was carried out in two areas of commercial production of muskmelons in the Mossoro-Assu-Baruna district, during two growth seasons from 2012-Jun to 2012-Nov. The components of energy balance and evapotranspiration were determined by using the Bowen Ratio Energy Balance method. It was observed that more than 60% of the net radiation (Rn) was converted into latent heat flux (lambda E), while 21 and 11% of Rn was converted into sensible heat flux (H) and soil heat flux (G), respectively. The ratio lambda E/Rn varies according to the change of leaf area index (LAI) while the ratios H/Rn and G/Rn vary inversely with the LAI. The agreement lambda E/Rn and LAI is also evidenced by similarity between curves of crop evapotranspiration (ETc) and LAI, particularly when the melon crop reaches its maximum vegetative growth (LAI > 3). The muskmelon ETc ranged from 265 to 289 mm, values that are similar to those found by other researcher.