Counts of “Persons of Spanish Surname” in the Southwestern United States were made by the U. S. Census in 1950 and are planned for 1960. Similar counts from other records can furnish numerators to go with denominators from the Census, but difficulties arise in explicit listing and definition of “Spanish Surname”. The problem was here approached from name counts of maiden surnames of mothers of infants with Spanish surnames. A log-normal distribution, fitted to this listing, allowed estimation of the number of names required for explicit listings having various proportions of coverage of all Spanish surnames. Since very long lists are required for high per cents of coverage, a 306-name list, with seventy per cent coverage, of a California population, is proposed for both Census and administrative use. Such a list would generate accurate rates for that portion of the population covered, even though the per cents covered might vary.