A thorough review of the Perkins instability is presented in this paper. We introduce two new elements to the earlier model presented by Perkins [1973>, namely, the neutral wind velocity and gradients in the background field line integrated density and Pedersen conductivity, respectively. We derive the eigenfrequencies and growth rates for a new instability and recover the limiting cases discussed by Perkins [1973> and Miller [1997>. The presence of gradients in the background density and Pedersen conductivity reveals a new branch in the dispersion relation and can possibly enhance the Perkins instability growth rate. The need for horizontal gradients, as was pointed out by Basu et al. [1981>, is essential for the generation of small-scale and kilometer-scale irregularities. The Perkins instability is shown to be enhanced by both the presence of a neutral wind and the background density and Pedersen conductivity. ¿ 1999 American Geophysical Union