Hydrophobins are small proteins secreted by filamentous fungi that have a unique ability to spontaneously form amphiphilic layers. Hydrophobins have only recently been structurally characterized through the first crystal structure determination of a protein of this class, Trichoderma reesei hydrophobin HFBII [Hakanpää, Paananen et al. (2004), J. Biol. Chem. 279, 534-539]. The resolution of the HFBII structure has now been extended to an ultrahigh resolution of 0.75 A. The structure was refined conventionally and multipole refinement has been initiated. The ultrahigh-resolution structure is analyzed here in detail and comparison is made to the previous atomic resolution structure of the same protein as well as to other ultrahigh-resolution structures found in the Protein Data Bank.