This paper presents some results of heat transfer deterioration (HTD) tests that were conducted on a finned smooth bore tube of 11 mm nominal ID to evaluate the effect of one-sided heating on the HTD phenomenon in once-through power boiler tubes, The one-side radiantly heated test sections were operated using upward steam-water flow at pressures of 179, 189, and 193 aim. Using peak heat flux at the tube wall crown as the correlating parameter and comparing with uniform heating data, the effects of one-sided healing on HTD quality and minimum heat transfer coefficient were found.