This study investigates the factors related to proficiency in understanding, speaking, reading, and writing English among immigrants using data from the 1992 National Adult Literacy Survey (NALS). It also investigates the earnings-English relationship for each of these four skills to establish which is more valuable in the labor market. English as a Second Language (ESL) courses, education, and years in the United States are found especially to affect English proficiency. Furthermore, the returns on oral proficiency are greater than the returns on literacy skills, although writing skills are more valuable than reading skills. The study concludes that English acquisition is a dynamic process, rather than static as argued by supporters of English-only legislation. An increased role for ESL courses in the acquisition of English is suggested as an alternative policy to English-only laws as long as the marginal cost is less than the marginal benefit.