The year 2002 marks the tenth anniversary of the discovery of the 'origin-recognition complex' — a key component in the initiation of DNA replication. Since that time, many advances have been made in various aspects of the replication process, both in prokaryotes and eukaryotes, and two of these advances are celebrated in this issue.

On page 826, Mike O'Donnell, John Kuriyan and colleagues describe the architecture and functioning of the so-called 'clamp loaders'. Replicative DNA polymerases owe their impressive ability to slide along great stretches of DNA to the ring-shaped clamps that attach them tightly to the template. These clamps are loaded onto the DNA by clamp loaders, which are composed of subunits that belong to the AAA+ ('ATPases associated with a variety of cellular activities') family and are conserved from archaea to eukaryotes. An elegant series of structural studies has now provided unique insights into how clamp loaders work, and how they might act to facilitate replication.

But what happens when, rather than being promoted, replication is stopped in its tracks by 'roadblocks' such as lesions in (or on) the DNA template? On page 859, Peter McGlynn and Robert Lloyd look at recent studies that describe how these blocks are removed and repaired, and how replication then restarts. Such studies are of interest as close links between DNA replication, recombination and repair have recently been uncovered in this process.

Finally, November 2002 marks another notable anniversary — the 90th birthday of George Palade. Palade's multidisciplinary view of the functional organization, biogenesis and dynamics of organelles has made a lasting impact on the field, and the Timeline article by Alan Tartakoff on page 871 celebrates his research, and his vital contributions to cell biology.