The bivariate lognormal distribution has been extensively utilized for modeling the fading gains of dual branch diversity receivers in both indoor and outdoor communication systems. The contribution of this letter is twofold: firstly, a general expression for the average bit-error probability (BEP) of diversity combining with two correlated lognormal fading branches is presented, based on a Gauss-Hermite sum approximation to the moment generating function. Secondly, using the proposed expression, it is shown that correlation can be viewed as an increase in the standard deviations of an equivalent diversity system with uncorrelated lognormal fading gains.