The structure of Canadian agriculture sector has changed significantly. There are fewer farms and farmers but the average farm size for those remaining has increased. The extent of the change varies by region and commodity. For example, average farm size has grown more in Saskatchewan than Ontario and the rate of growth is higher for hog farms than for other livestock farms. The growth in the average farm size is driven by an increase in the absolute number of large farms but the growing share of small farms tempers the extent of the increase in average farm size. Regardless of sector, the number of mid-sized farms that dominated production a generation ago has declined significantly. The hollowing out of the middle has resulted in a movement away from a bell-shaped distribution for farm size to a more uniform distribution. Those in the largest size categories consequently represent a growing percentage of total farm sales. In addition to size, which has been the focus of this review, farm structure can also be assessed in terms of by attributes such as specialization, focus, contracts, ownership structure, and markets. These attributes have also changed resulting in a sector with a heterogeneous group of participants. The variation makes it difficult to assess the need for policy action and what should be the focus of any interventions. The growing heterogeneity also suggests that there are different drivers for entry and exit within the sector and that understanding those drivers will help explain the underlying structural changes in agriculture.