Rapeseed is very widely cultivated throughout the world for the production of animal feed, vegetable oil for human consumption, and biodiesel; leading producers include the European Union, Canada, the United States, Australia, China and India. In India, it is grown on 13% of cropped land. According to the United States Department of Agriculture, rapeseed was the third leading source of vegetable oil in the world in 2000, after soybean and oil palm, and also the world's second leading source of protein meal, although only one-fifth of the production of the leading soybean meal. World production is growing rapidly, with FAO reporting that 36 million tonnes of rapeseed was produced in the 2003-4 season, and 46 million tonnes in 2004-5. In Europe, rapeseed is primarily cultivated for animal feed (due to its very high lipid and medium protein content), and is a leading option for Europeans to avoid importation of GMO products.

Natural rapeseed oil contains erucic acid, which is mildly toxic to humans in large doses but is used as a food additive in smaller doses. Canola is a tradename for low erucic acid rapeseed that is sometimes mis-applied to other cultivars.

The rapeseed is the valuable, harvested component of the crop. The crop is also grown as a winter-cover crop. It provides good coverage of the soil in winter, and limits nitrogen run-off. The plant is ploughed back in the soil or used as bedding

Processing of rapeseed for oil production provides rapeseed animal meal as a by-product. The by-product is a high-protein animal feed, competitive with soya. The feed is mostly employed for cattle feeding, but also for pigs and chickens (though less valuable for these). The meal has a very low content of the glucosinolates responsible for metabolism disruption in cattle and pigs. Rapeseed "oil cake" is also used as a fertilizer in China, and may be used for ornamentals, such as Bonsai, as well.

Rapeseed leaves and stems are also edible, similar to those of the related bok choy or kale. Some varieties of rapeseed (called ??, yóu cài, lit. "oil vegetable" in Chinese; yu choy in Cantonese; and ???, nanohana in Japanese) are sold as greens, primarily in Asian groceries.

Rapeseed is a heavy nectar producer, and honeybees produce a light colored, but peppery honey from it. It must be extracted immediately after processing is finished, as it will quickly granulate in the honeycomb and will be impossible to extract. The honey is usually blended with milder honeys, if used for table use, or sold as bakery grade. Rapeseed growers contract with beekeepers for the pollination of the crop.

Rapeseed oil is used in the manufacture of biodiesel for powering motor vehicles. Biodiesel may be used in pure form in newer engines without engine damage, and is frequently combined with standard diesel in ratios varying from 2% to 20% biodiesel. Formerly, due to the costs of growing, crushing, and refining rapeseed biodiesel, rapeseed derived biodiesel cost more to produce than standard diesel fuel. Prices of rapeseed oil are at very high levels presently (start November 05) due to increased demand on rapeseed oil for this purpose. Rapeseed oil is the preferred oil stock for biodiesel production in most of Europe, partly because rapeseed produces more oil per unit of land area as compared to other oil sources, such as soy beans.

Rapeseed has been linked with adverse effects in asthma and hay fever sufferers.[citation needed] Some suggest that oilseed pollen is the cause of increased breathing difficulties.[citation needed] This is unlikely however, as rapeseed is an entomophilous crop, with pollen transfer primarily by insects. Others suggest that it is the inhalation of oilseed rape dust that causes this, and that allergies to the pollen are relatively rare.[citation needed] There may also be another effect at work; since rapeseed in flower has a distinctive and pungent smell, hayfever sufferers may wrongly jump to the conclusion that it is the rapeseed that is to blame simply because they can smell it.

The Monsanto Company has genetically engineered new cultivars of rapeseed that are resistant to the effects of the herbicide Roundup. They have been vigorously prosecuting farmers found to have the Roundup Ready gene in Canola in their fields without paying a license fee. These farmers have claimed the Roundup Ready gene was blown into their fields and crossed with unaltered Canola. Other farmers claim that after spraying Roundup in non-Canola fields to kill weeds before planting, Roundup Ready volunteers are left behind, causing extra expense to rid their fields of the weeds.

In a closely followed legal battle, the Supreme Court of Canada found in favor of Monsanto's patent infringement claim for illegal growing of Roundup Ready in its 2004 ruling on Monsanto Canada Inc. v. Schmeiser. The case garnered international controversy as a court-sanctioned legitimation for the global patent protection of genetically modified crops.

There is also major concern that the extensive use of herbicide led to significant loss of biodiversity as wildflowers are killed, leaving other wildlife dependent on the wildflowers unable to survive.

Worldwide production of rapeseed (including canola) rose to 46.4 million metric tons in 2005, the highest recorded total.