Morphological studies have been considered very important in fungal fermentation. Morphological parameters and the type of mycelia present (free mycelia without any branches, branched mycelia and branched mycelia with conidiophore) were measured to correlate citric acid production with the morphology of Aspergillus niger. We observed that morphological parameters and the type of mycelia present varied with substrate concentration. They also depended on the type of substrate (molasses and glucose) used. Maximum citric acid (6.8 kg/m3) was produced when branched mycelia with conidiophore were the most available mycelia present in the broth of molasses containing medium. Citric acid was produced in lesser quantity (1.82 kg/m3) when glucose was used. The addition of methanol doubled citric acid production, increased slightly the percentage of branched mycelia with conidiophore and conditioned the surface of the mycelia.