Abstract The reaction of a ten-fold excess of NaH with p-tert-butylcalix [4] arene in THF results in the mono-oxyanion, [Na(MeOH)(H2O)2][p-tert-butylcalix [4] arene] · H2O·MeOH, 1. The compound crystallizes in the monoclinic space group P21/n with a = 12.982(5), b = 19.236(8), c = 21.763(8) A, β = 94.77(4)° and Dc = 0.97 g cm−3 for Z = 4. Refinement based on 2722 observed reflections led to a final R value of 0.099. The similar reaction of LiH with p-tert-butylcalix [4]arene affords as the only product the di-oxyanion, [(Li(MeOH))2(μ-H2O)][p-tert-butylcalix [4] arene]·2H2O·3MeOH, 2. The compound crystallizes in P21/n with a = 12.420(6), b = 21.656(9), c = 21.172(9) A, β = 108.14(5)°, and Dc = 1.08 g cm−3 for Z = 4. Refinement based on 2215 observed reflections led to a final R value of 0.13. The calix [4] arene cavity in both 1 and 2 contains a methanol molecule. The failure to generate tri- or tetra-oxyanions is rationalized on the basis of electrostatic considerations.