The genes for G protein-coupled receptors (GPCRs) including those encoding the classical mu, delta, and kappa opioid receptors (MOR, DOR, and KOR); cannabinoid receptors (CB1); ACTH receptor (melanocortin receptor type 2, MC2R); and serotonin receptors (5HT1B) have been a focus of the studies of our group for a number of years since these receptors are involved in specific addictions. Genetic variants of GPCR genes have been associated with vulnerability to stress, anxiety, depression, and predisposition to develop drug addiction. To study these variants including single nucleotide polymorphisms (SNPs) and their allocation on alleles (haplotypes), our group developed special techniques (genotyping assays using polyacrylamide gel pad technology, molecular haplotyping assays based on the use of fluorescent PCR) and also used commercially available techniques and methodologies. Although these novel technologies allow rapid and reliable high-throughput analysis, in order to use them, the precise position of the polymorphic site should be known in advance. The contemporary genetic databases contain copious information on genetic variants. However, we found that some important functional variants are still unreported. Therefore, resequencing of the genes studied in specific populations is necessary. Each technology that we use has specific advantages that we will discuss below.