Sociological researchers have studied the consequences of strong categorical boundaries, but have devoted little attention to the causes and consequences of boundary erosion. This study analyzes the erosion of categorical boundaries in the case of opposing category pairs. The authors propose that categorical boundaries weaken when the borrowing of elements from a rival category by high-status actors triggers emulation such that the mean number of elements borrowed by others increases and the variance in the number of elements borrowed declines. It is suggested that penalties to borrowing in the form of downgraded evaluations by critics exist, but decline as the number of peers who borrow increases. The research setting is French gastronomy during the period from 1970 to 1997, when classical and nouvelle cuisines were rival categories competing for the allegiance of chefs. The results broadly support the authors’ hypotheses, indicating that chefs redrew the boundaries of culinary categories, which critics eventually recognized. Implications for research on blending and segregating processes are outlined.