Germinal centres (GCs) are involved in the selection of B cells secreting high-affinity antibodies and are also the origin of most human B cell lymphomas. Recent progress has been made in identifying the functionally relevant stages of the GC and the complex trafficking mechanisms of B cells within the GC. These studies have identified transcription factors and signalling pathways that regulate distinct phases of GC development. Notably, these factors and pathways are hijacked during tumorigenesis, as revealed by analyses of the genetic lesions associated with various types of B cell lymphomas. This Review focuses on recent insights into the mechanisms that regulate GC development and that are relevant for human B cell lymphomagenesis.