Formation of phases developing by solid-state reaction in Al thin film and Pt vapour beam is reported. The samples have been studied by high temperature sequential deposition (HTSD) [Mat. Sci. Forum, 22–24 (1987) 617]. The Al and Pt were deposited by e-beam evaporation on a-C layers supported by TEM microgrids in an UHV system. A special evaporation arrangement made possible to visualise the sequentially forming phases side by side by creating wedge-shaped area with increasing Al film thickness in the half shadow of the sample holder. By changing the quantity of elements available for the reaction the sequences of intermetallic Al3Pt2, AlPt2, and AlPt3 phases have been found. The samples were investigated by electron microscopy techniques (TEM, SAED, EDS). The electron diffraction patterns have been evaluated by the ProcessDiffraction program [J.L. Lábár in Proc. XII. EUREM, Brno, July 9–14, 2000, I 379].