The approach to the main sequence of stars in the mass range 0.060.2 M0 has been investigated for the composition X = 0.68, F = 0.29, and Z = 0.03. The theoretical main sequence in the spectral range M4M8 has been determined for t/Hp ratios of 1 and 2, and its position in the H-R diagram has been found to be practically independent of the I/Hp ratio. The agreement between the theoretical and the observational main sequence in the region is examined, and it is found that the star models calculated here are consistent with the observations. The age of stars on the main sequence in the M8 region is on the order of 10 years. We estimate the main-sequence mass limit at the composition given above to be 0.075 M0. The evolution of a 0.1 M0 star is studied in detail in order to determine the role played by chemical composition in determining the lower mass limit of the main sequence and the effects of primordial deuterium and lithium burning. At the above composition the 0.1 M0 star does reach a stable mainsequence stage for both 1/Hp = 1 and I/Hp = 2. With an XD = 0.19 X 10-i, the primordial deuterium burning increases the approach time to the main sequence by about 106 years. Electron-screening factors which have been scaled for the intermediate cases between weak and strong screening have been used to calculate the nuclear-reaction rates at 0.1 Af0. The effects of water-vapor opacity and pressure ionization and dissociation have been included in the star-model calculations.