The linewidth of a LAMBDA-type noninversion laser is calculated on the
basis of a c-number Langevin approach in lowest order of the laser fi
eld. It is shown that the system behaves in general-that is, also in t
he good-cavity limit-nonadiabatically. In the nonadiabatic regime a su
bstantial deviation of the laser linewidth from the Schawlow-Townes fo
rmula is found and a simple interpretation is given.