An intense, space‐charge‐neutral beam of protons (150 kV, 15 A/cm2) has been compressed from an initial diameter of 15 cm to a final diameter of 5 cm by propagating it along a magnetic field increasing from zero to 700 G in a distance of 55 cm. At the field maximum, the beam intensity is increased by a factor of 4 over the value with no field. When viewed from the beam frame, the experiment is analogous to a theta pinch with an applied field whose time derivative isv(dB/dx), wherevis the beam velocity anddB/dxis the magnetic gradient. The surface of the beam moves radially inward at approximately the velocity predicted by the snowplow model.