Efficient monitoring for the emergence of resistance to various antimicrobial agents has, in the face of global trends in resistance, recently assumed great importance. Many programmes have been developed to survey resistance, each varying in scope or emphasis as well as commitment to long-term monitoring. A programme that specifically addresses pathogens from populations of the most severely ill patients is the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC). This programme was started in 1997 to monitor carbapenem activity in vitro in centres using carbapenems because their prevalent strains were resistant to other β-lactams and drug classes. Meropenem is a broad-spectrum carbapenem and differs microbiologically from imipenem by having a greater potency in vitro against many Gram-negative pathogens and a slightly lower potency against some Gram-positive pathogens. Meropenem has improved stability to renal-based enzymatic metabolism, and does not require the addition of an enzyme inhibitor such as cilastatin. Material in this publication is based on the many abstracts and oral presentations delivered at recent national and international meetings including: the International Congress of Infectious Disease in Buenos Aires, Argentina (April, 2000); the European Congress of Chemotherapy in Madrid, Spain (May, 2000); and the European Congress of Clinical Microbiology and Infectious Disease in Stockholm, Sweden (May, 2000). All of the authors are active participants in the MYSTIC programme and bring to it experience in the design of surveillance studies and the detection of resistance mechanisms. Professor Jones discusses the most useful ways of storing and presenting susceptibility data to preserve the long-term value of all results. He argues for the publication of expanded study details and the limited use of MIC90 values or susceptibility rates. Dr Turner has coordinated the MYSTIC programme, and he summarizes here the similarities and differences in the results seen to date between the Americas, Europe and centres in Asia and the Middle East. The Americas have been one of the most recently monitored regions. Professors Pfaller and Jones give baseline data for the USA (10 sites), Mexico and Brazil. Professor Goossen's article focuses on the results of MYSTIC in the European centres. Doctor Masterton presents a comprehensive overview of various surveillance studies and assesses their value and characteristics for the continued optimal management of infected patients.