In March 1978 there were 12 million persons of Spanish origin in the United States: about 7.2 million of Mexican origin, 1.8 million of Puerto Rican origin, 700,000 of Cuban origin, 900,000 of Central or South American origin, and about 1.5 million of other Spanish origin. Of these, 85% resided in metropolitan areas. About 42% were under 18 years old, while only about 4% were 65 years old and over. Among those 25 to 29 years old, 57% had a high school education, as compared with only 30% of those 45 to 64 years old. About 21% of the families had incomes below the poverty level in 1977; only 9.7% had incomes of $25,000 or more. About 80% of the men were in the civilian labor force compared with 45% of the women. The median income for the men was $7,797 while the median income of the women was $3,669. Although both men and women of Spanish origin were about equally likely to be currently married in March 1978, the men were more likely than the women to have never been married, and the women were more likely than the men to be either widowed or divorced. This report presents advance data, collected in March 1978 by the Census Bureau, on the demographic, social and economic characteristics of persons of Spanish origin. Characteristics presented include age, sex, marital status, educational attainment, employment status, occupation, and income. Data on residence, income, and poverty status are shown for families of Spanish origin. (NQ)