Poly(di-n-hexylsilane) (PDHS) films cast at various conditions from toluene solutions were studied by X-ray diffraction, d.s.c.. u.v.-vis. spectroscopy and fluorescence spectroscopy. The higher-order structure of cast films is discussed in relation to their phase transitions. Films dried slowly at 2 degrees C (film a), quickly at room temperature (film b) and slowly at 36 degrees C (films c and d) have low, moderate and highly crystalline structures, respectively. Tn thin film c, the (110) plane of the orthorhombic unit cell is oriented parallel to the film surface. The u.v. absorption maxima due to the ordered phase were observed around 357 nm (film a), 370 nm (film b) and 375 nm (film c). The peaks in the fluorescence spectra were observed between 350 nm and 389 nm. The d.s.c. peak temperature for phase transition was observed at 36-49 degrees C.