Radiation pressure due to absorption in spectral lines can play an important role in the equilibrium conditions in the outer portions of the stellar atmosphere. In particular, it is suggested that spicules ejected from the upper solar chromosphere as well as other fine structural features of the chromosphere may very likely be a result of radiation pressure from Ly-a. Numerical computation of the radial radiation pressure due to Ly-α in the chromospheric model of Vernazza et al. (1973) gives a maximum outward pressure gradient due to radiation that is 0.06 of the gravitational pressure gradient. The model chromosphere of Vernazza et al. is a spherically symmetric model that reproduces the average Sun Ly-α intensity and profile. Supergranule borders (network), where spicules arise, are known to have a Ly-α brightness some ten times the average Sun brightness. It is suggested, therefore, that in the network areas the pressure gradient due to radiation is comparable to (and oppositely directed to) that due to gravitation and that in local areas of unusual brightness the net pressure gradient is outwards. An estimate of the expected outwards velocity of spicule material driven by radiation pressure was made by equating the kinetic energy flux (½JϱV3) to the Ly-α energy flux. This gives values of v that are comparable to observed spicule velocities. Also, the maximum outwards radiation pressure occurs in the upper chromosphere where the material density in the model of Vernazza et al. is close to the value 4 × 10−14 g cm−3, which is about a factor of two less than the currently accepted value for spicules. Increased density in the network areas could easily remove this minor difference.