Reproduction in teleosts is controlled by the hypothalamo-pituitary – gonadal (HPG) axis. Under the control of the hypothalamic hormones especially the gonadotropin - releasing hormone (GnRH), the pituitary secretes gonadotropins for release physiological actions on gonads. They are glycoprotein hormones secreted by the gonadotropes present in the pars distalis. The duality of pituitary gonadotropin is a common feature in all gnathostome vertebrate groups. The gonadotropes secrete two gonadotropins formed by a shared α-subunit (GPα), non-covalently linked to a specific β-subunit. Functionally these are classified as FSH and LH, and are critical regulators of gametogenesis. Each subunit (GPα, FSHβ and LHβ) is encoded by a distinct gene. The β –subunit renders the functional specificity of the molecule. To date, cDNA sequences encoding gonadotropin subunits have been isolated and characterized from more than 56 fish species, representing at least 14 Orders. Catfish is an important emerging aquaculture species in India with great economic potential. The catfish Heteropneustes fossilis is a highly demanding freshwater air-breathing fish species in the Indian subcontinent and South East Asian region. Breeding and propagation of catfish in captivity is a great challenge, and securing better control over reproductive processes is a time demand. The gonadotropin subunits are an interesting group of molecules not only because of their importance in reproduction and overall physiology but also because of their unique structural features and phylogeny. The gonadotropins exhibit a remarkable conservation in their structural organization, implying a common origin from the earliest ancestors. Recently, using molecular cloning techniques we isolated catfish gonadotropin subunits GPα, FSHβ and LHβ, encoded by distinct genes, yielding predicted proteins of 116, 132 and 138 amino acid residues, respectively. Further, these subunits were studied for elucidation of phylogenetic relationship together with their structural and biological characteristics.