β-lactams have been consistently associated with the majority of drug-related adverse events. Generally, these are mild under proper dosing and judicious selection. Immediate hypersensitivity reactions are the most feared adverse events encountered after β-lactam administration. Emerging evidence shows that immediate reactions are not as common as previously thought. Specialist consultation and testing seems prudent before a patient is officially declared allergic to β-lactams. The risk of cross-reactions between not only members of the β-lactam super-family but also between specific classes is also lower than previously thought. Newer studies have shown that cross-reactions are not universal and pertain to specific agents with similar side chains or metabolites of the β-lactam core. The frequency of severe kidney or liver toxicity, neurotoxicity, cytopenias and Clostiridium difficile infection following β-lactam administration seem to be agent-specific. The currently available data denote that in addition to age, gender, co-morbidity, renal or liver function, and co-administered agents, the antibiotic levels rather than the dose itself seem to be associated with the emergence of adverse events. Most of them subside with time after withdrawal of the offending agent, but the number of cases resulting in chronic disabilities or even deaths in not negligible.