The temporal and spatial control of auxin distribution has a key role in regulating plant growth and development, and much has been learnt about the mechanisms that influence auxin pools and gradients in vegetative tissues, particularly in Arabidopsis. For example, polar auxin transport mediated by PIN and AUX/LAX proteins, is central to the control of auxin distribution. In contrast, very little is known about the dynamics of auxin distribution and the molecular basis of its transport within and between fruit tissues, despite the fact that auxin regulates many aspects of fruit development, including fruit formation, expansion, ripening and abscission. In addition, functional information regarding the key regulators of auxin fluxes during both vegetative and reproductive development in species other than Arabidopsis is scarce. To address these issues, we have investigated the spatiotemporal distribution of auxin during tomato (Solanum lycopersicum) fruit development and the function of the PIN and AUX/LAX gene families. Differential concentrations of auxin become apparent during early fruit growth with auxin levels being higher in internal tissues than in the fruit pericarp and the pattern of auxin accumulation depended on polar transport. Ten tomato PIN (SlPIN1 to 10) and five AUX/LAX (SlLAX1 to 5) genes were identified and found to display heterogeneous expression patterns, with tissue and developmental-stage specificity. RNAi mediated co-silencing of SlPIN4 and SlPIN3 did not affect fruit development, suggesting functional redundancy of PIN proteins, but did lead to a vegetative phenotype, revealing a role for these genes in regulating tomato shoot architecture. © 2011 The Authors. The Plant Journal© 2011 Blackwell Publishing Ltd.