Strains of Neisseria gonorrhoeae that are resistant to antimicrobial agents have emerged after the use of these agents. Antimicrobial resistance can be either chromosomal or plasmid-mediated. Arbitrary methods, both agar-dilution and disk-diffusion procedures, have been developed to measure the in-vitro antimicrobial resistance of gonococcal isolates. These methods must be performed by use of standard procedures and the quality of the process must be controlled by use of reference strains with known susceptibilities. Results of antimicrobial susceptibility tests must be interpreted with caution. Phenotypic characterization of gonococcal isolates using auxotyping, serotyping, and plasmid content has permitted us to compare susceptible and resistant strains in an effort to understand the diversity of antimicrobial resistance in N. gonorrhoeae and the dynamics of epidemics of gonorrhoea associated with resistant strains.