The vertical gradients of meiofauna mainly in relation to biochemical changes and microbial abundance in the upper 20 cm of deposit of a mangrove mud flat were studied. Strong vertical gradients in the redox potential (Eh), interstitial water and sedimentary organic compounds were recorded. Microbial and phytobenthos also showed clear vertical gradients and a significant number of bacteria were encountered in the 15-20 cm depth. Abundance of meiofauna followed distinct vertical gradient and the number decreased significantly with increasing depth in the sediment. The reducing environment was characterisEd. by high population of nematodes, turbellarians and harpacticoids. Merofaunal taxa were significantly correlated with Eh and interstitial water of the sediment. Among the meiofaunal food, organic matter, ATP phytobenthic abundance and bacterial counts were positively correlated with meiofaunal density. Biochemical constituents did not yield any significant correlation with meiofauna. Food availability played a supporting role while physical environmental parameters were more important in meiofaunal dispersion in mangrove mud flats