The three largest sectors of San Diego's economy are defense, manufacturing, and tourism respectively.
Several areas of San Diego (in particular La Jolla and surrounding Sorrento Valley areas) are home to offices and research facilities for numerous biotechnology companies.
Major biotechnology companies like Neurocrine Biosciences and Nventa Biopharmaceuticals are headquartered in San Diego, while many biotech and pharmaceutical companies, such as BD Biosciences, Biogen Idec, Integrated DNA Technologies, Merck, Pfizer, Élan, Genzyme, Cytovance, Celgene and Vertex, have offices or research facilities in San Diego.
There are also several non-profit biotech institutes, such as the Salk Institute for Biological Studies, the Scripps Research Institute and the Burnham Institute. The presence of University of California, San Diego and other research institutions helped fuel biotechnology growth.
In June 2004, San Diego was ranked the top biotech cluster in the U.S. by the Milken Institute.
San Diego is home to companies that develop wireless cellular technology.
Qualcomm Incorporated was founded and is headquartered in San Diego; Qualcomm is the largest private-sector technology employer (excluding hospitals) in San Diego County.
The largest software company in San Diego (according to the San Diego Business Journal) is security software company Websense Inc.
The economy of San Diego is influenced by its port, which includes the only major submarine and shipbuilding yards on the West Coast, as well as the largest naval fleet in the world. The cruise ship industry, which is the second largest in California, generates an estimated $2 million annually from the purchase of food, fuel, supplies, and maintenance services.
Due to San Diego's military influence, major national defense contractors, such as General Atomics and Science Applications International Corporation are headquartered in San Diego.
Tourism is also a major industry owing to the city's climate.
Major tourist destinations include Balboa Park, the San Diego Zoo, Seaworld, nearby Wild Animal Park and Legoland, the city's beaches and golf tournaments like the Buick Invitational.