SYNOPSIS. Maternal effects comprise a class of phenotypic effects that parents have on phenotypes of their offspring that are unrelated to the offspring's own genotype. Although biologists have known about the importance of these effects for decades, maternal effects have only recently been studied widely by evolutionary ecologists. Moreover, the impact of maternal effects on the rate and direction of evolution of other components of the phenotype has only recently been fully elucidated by theoretical genetic models. This paper provides a brief overview of maternal effects research, focusing on research conducted in animal systems. First, I review and summarize definitions and theoretical treatments of maternal effects. Then I survey the diversity of maternal effects and some of the kinds of ecological and evolutionary impacts that maternal effects have been shown to have on offspring performance. Third, I discuss some of the ecological and evolutionary implications of maternal effects in ecological research. In this context, it is argued that the kinds of maternal effects that have been studied, and some of the potential implications of maternal effects that have not been explored are both artifacts of research effort. Hence, I identify several fruitful areas for future maternal effects research. Lastly, I describe the necessity of explicitly incorporating maternal effects in ecological research, whether or not the researcher is focusing on them as the topic of the research.