The myxobacteria are Gram-negative organisms that are capable of multicellular, social behaviour. In the presence of nutrients, swarms of myxobacteria feed cooperatively by sharing extracellular digestive enzymes, and can prey on other bacteria. When the food supply runs low, they initiate a complex developmental programme that culminates in the production of a fruiting body. Myxobacteria move by gliding and have two, polarly positioned engines to control their motility. The two engines undergo coordinated reversals, and changes in the reversal frequency and speed are responsible for the different patterns of movement that are seen during development. The myxobacteria communicate with each other and coordinate their movements through a cell-contact-dependent signal. Here, the cell movements that culminate in the development of the multicellular fruiting body are reviewed.