  Searching for main-sequence pulsators, we analyzed photometry of ~200,000
variable star candidates from the OGLE-II Galactic fields, finding 193
high-amplitude Delta Scuti stars. This doubles the number of known stars of
this type. The MACHO data, available for half of stars, were also analyzed. In
our sample of the HADS stars, we found 50 multiperiodic objects, including 39
that have period ratios in the range of 0.76-0.80, an indication of the radial
fundamental and first-overtone pulsation. We discuss the resulting Petersen
diagram for these stars in view of the period ratios predicted by models.
Except for stars showing pulsations in the radial fundamental mode and first
overtone, we find the evidence for higher radial overtones and non-radial modes
in the analyzed sample of multiperiodic HADS stars.
