The drug market has seen a significant global expansion in the last decades. The synthetic designer drugs belonging to the class of amphetamines and derived phenylethylamines have experienced the greatest spread in the drug market for abuse. As phenylethylamines are organic compounds that stimulate the central nervous system of humans, many are abused as recreational drugs. A large array of substituted amphetamines can be easily synthetized by replacing one or more hydrogen atoms in the structure of phenylethylamine. Among these, the most dangerous for human health are those analogues or homologues that have hallucinogenic effects (besides the stimulant pharmacological activity), such as those belonging to the 2C-x and DOx classes of amphetamines. This review describes the physico-chemical and spectral properties of the most representative compounds of the two classes.