We demonstrate that the spatial mode of high-order harmonics can be co
ntinuously controlled. The control is achieved by spatially modulating
the degree of elliptical polarization of the fundamental field using
birefringent optics. A highly sensitive relationship between the effic
iency of harmonic generation and the degree of laser elliptical polari
zation leads to atoms emitting harmonics mainly in regions of linear p
olarization. The harmonics are emitted as annular beams whose angles o
f divergence can be continuously varied.