An experimental study on dryout characteristics of helically coiled tubes was conducted by measuring wall temperature fluctuations near the dryout point. The region where the wall temperature fluctuations were observed in the coiled tube was wider than that in a straight tube. Circumferential wall temperature differences near the dryout point became significant when the coil diameter was small and the mass flow rate was low. The dryout mechanism in the coiled tube was discussed on the basis of the flow pattern map constructed by the author's air-water experimental results. Critical heat fluxes in helically coiled tubes, which were higher than that in a straight tube, were compared with empirical correlations. Comparing the present results with Katto's correlation for a straight tube, a modified correlation was presented.