The prediction of Roppo, Davis, and Rosenblat [Phys. Fluids27, 796 (1984)] that hexagons should appear near threshold in a Rayleigh–Be´nard cell under external modulation of the temperature is reconsidered with a view to determining the experimental observability of the effect. It is found that in the limit of low‐modulation amplitude &dgr; considered by Roppoetal. the effects are qualitatively as given by these authors, but considerably smaller quantitatively. The validity limits of the small‐&dgr; expansion are clarified and results of an alternative theory of hexagonal effects, valid at arbitrary amplitude &dgr; and frequency &ohgr;, are briefly summarized. Hexagons will only be observable if large amplitudes can be achieved.