Abstract: The question "Does initial marginal quality of composite restorations have any affect on clinical longevity?" is posed and evidence presented to attempt to provide an answer. This paper examines the literature on what is known regarding the rates and causes of failure of restorations, clinical evaluation of restoration outcomes and marginal quality, the relationship between marginal quality and secondary caries, and the relationship of polymerization shrinkage and clinical failures. The most frequently reported cause for restoration replacement is secondary caries. The evidence that poor marginal quality promotes or is the primary cause for secondary caries is limited and indicates that any direct relationship is unlikely. There is evidence that secondary caries is related to the bacterial composition of marginal plaque, and that this and oral hygiene are the primary factors in disease initiation. Evidence also exists that dentists vary in their diagnoses of secondary caries and that except in the presence of frank secondary caries, it is not possible to diagnose secondary caries with high sensitivity and specificity based on visual and tactile examination of restoration margins. Marginal gaps created by polymerization shrinkage do not appear to increase the risk for secondary caries, but can lead to marginal staining. Initial marginal quality should not affect longevity, as it does not necessarily increase the risk of secondary caries. However, poor marginal quality is, in fact, likely to decrease clinical longevity due to the misdiagnosis of secondary caries. Schlagwörter: dental, restoration, margin, clinical.