We investigate analytically and experimentally various aspects of the angul
ar chirp of ultrashort laser pulses. This type of chirp is easily produced
by slight misalignment of standard pulse stretcher and/or compressor setups
. Angular chirp leads to tilted pulse fronts in the near field and to a str
ong reduction of intensity in the focus. The effect is rather difficult to
observe with standard diagnostic techniques. We present a method that is ba
sed on interferometric field autocorrelation and allows us to measure the a
ngular chirp reliably. Suggestions on how to avoid this effect are outlined
as well.