The investigation of hormone and neurotransmitter receptors has become one of the most active areas in biochemical and biomedical research. This chapter provides a general review of production of G protein-coupled receptors (GPCRs) in the yeast system and compare it with other expression systems. It discusses some essential recipes for GPCR production using the Pichia pastoris expression system. Adrenergic receptors, also named adrenoceptors, bind the catecholamines adrenaline and noradrenalin. Both catecholamines act as neurotransmitters in the sympathetic nervous system. Opioid receptors are part of a neuromodulatory system that plays a major role in the control of nociceptive pathways. Production of GPCRs in yeasts is yet at the beginning. Screening systems based on yeasts have the advantage of fast and easy handling. In conclusion, yeast-based expression systems have had and will have a great impact on revealing the secrets of G protein-coupled receptors.