The cubic phase of tetraamminelithium(zero), Li(NH3)4, has been stabilized below the normal solid−solid transition temperature by freezing lithium−ammonia solutions more dilute than 0.2 MPM. Conduction electron spin resonance (CESR) has been studied in the temperature range 11−160°K. CESR line shapes are in excellent agreement with Webb’s theoretical line−shape function. The relative resistivity, average particle size g shift, spin−lattice relaxation time, and relative paramagnetic susceptibility are extracted from the CESR spectra. The resistivity varies linearly with temperature down to 11°K; on the basis of the Block−Grüneisen theory, it is estimated that the Debye temperature is below 30°K. Average particle sizes are in the micron range. The g shift is temperature independent and equal to −8.3±0.3×10−4. For concentrations exceeding 0.01 MPM the spin−lattice relaxation rate varies linearly with temperature down to 11°K. Surface relaxation becomes important below 0.01 MPM. The impurity, surface, and bulk spin−lattice relaxation times are separated in a 0.001 MPM sample. Several spin−lattice relaxation mechanisms are evaluated, and it is concluded that the spin−orbit relaxation mechanism is dominant. The paramagnetic susceptibility of the cubic phase is temperature independent; it undergoes an 8% increase at the melting point, attributable to the decrease in density upon melting. In contrast to the hexagonal phase of Li(NH3)4, the cubic phase exhibits normal metallic behavior.