Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; The aim of this study was to investigate (i) the influence of potassium stress through two potassium fertilizer (KCl and K(2)SO(4)) treatments over leaf proline and fruit production in eggplant, as well as (ii) the modifications in electrical conductivity of soil. The experiment design used was factorial scheme with randomized blocks, 2 potassium sources (KCl and K(2)SO(4)) combined with 4 levels of K(2)O (250, 500, 750 and 1000 kg ha(-1)). The highest fruit production was obtained with K(2)O 500 kg ha(-1) using KCl compared to K(2)SO(4) with an average electrical conductivity of 2.76 and 2.16 dS m(-1). In this study it was observed that excessive level of KCl and K(2)SO(4) as K(2)O 1000 kg ha(-1) resulted in decrease of fruit production and increase of proline concentration in leaves of the eggplant.