The census of 2000 recorded 3,694,820 people, 1,275,412 households, and 798,407 families residing in the city, with a population density of 7,876.8 people per square mile (3,041.3/km²). There were 1,337,706 housing units at an average density of 2,851.8 per square mile (1,101.1/km²). Los Angeles has become a multiethnic/diverse city, with major new groups of Latino and Asian immigrants in recent decades. As of the 2000 US Census, the racial distribution in Los Angeles was 46.9% White American, 11.2% African American, 10.5% Asian American, 0.8% Native American, 0.2% Pacific Islander, 25.7% from other races, and 5.2% from two or more races. 46.5% of the population was Hispanic or Latino (of any race).

42.2% spoke English, 41.7% Spanish, 2.4% Korean, 2.3% Filipino, 1.7% Armenian, 1.5% Chinese (including Cantonese and Mandarin) and 1.3% Persian as their first language. Since the mid-1980s, Los Angeles has been a minority-majority city.

According to the census, 33.5% of households had children under 18, 41.9% were married couples, 14.5% had a female householder with no husband present, and 37.4% were non-families. 28.5% of households were made up of individuals and 7.4% had someone living alone who was 65 years of age or older. The average household size was 2.83 and the average family size 3.56.

The age distribution was: 26.6% under 18, 11.1% from 18 to 24, 34.1% from 25 to 44, 18.6% from 45 to 64, and 9.7% who were 65 or older. The median age was 32. For every 100 females there were 99.4 males. For every 100 females aged 18 and over, there were 97.5 males.

The median income for a household was $36,687, and for a family was $39,942. Males had a median income of $31,880, females $30,197. The per capita income was $20,671. 22.1% of the population and 18.3% of families were below the poverty line. 30.3% of those under the age of 18 and 12.6% of those aged 65 or older were below the poverty line.

Los Angeles is home to people from more than 140 countries speaking 224 different identified languages. Ethnic enclaves like Chinatown, Historic Filipinotown, Koreatown, Little Armenia, Little Ethiopia, Tehrangeles, Little India, Little Tokyo and Thai Town provide examples of the polyglot character of Los Angeles.