The electronic properties of the alkali trimers Li3, Na 3, and K3 are studied using the pseudopotential and the local-spin-density approximations. More than 100 configurations were calculated for each trimer in order to obtain a complete picture of the adiabatic Born-Oppenheimer surfaces. The equilibrium geometry of the trimers are Jahn-Teller distortions of an equilateral triangle. Although the three surfaces are quite similar, Li3 is more affected than Na3 or K 3 by the dynamical character of the Jahn-Teller distortion. The calculated ionization potentials agree very well with the experimental values and the qualitative features of the Born-Oppenheimer surface are confirmed by recent ESR experiments. © 1983 American Institute of Physics.