Between 1990 and 2000, the Hispanic population of the West increased by 54 percent, compared to a 13 percent increase for non-Hispanics. The Hispanic population now represents 25 percent of the West's population, up from 19 percent in 1990. This information brief describes the increase in Hispanic populations in the West from 1990 to 2000 and discusses the impacts of increasing diversity on 11 western states: Montana, Wyoming, Colorado, Arizona, Idaho, Utah, Nevada, New Mexico, California, Washington, and Oregon. Primarily of Mexican origin, the West's Hispanics have increased due to both immigration and natural increase. Noteworthy features of the West's Hispanic population is that it is becoming younger, is becoming more rural, is seeking entry-level jobs, and is unevenly distributed geographically. The impact of these changes will be multi-faceted and will include pressure on schools to accommodate growing numbers of Spanish-speaking students and parents. The fact that growth is proportionately more rapid in rural places means that affected schools may already be cash-poor and may need additional resources to serve these students. The youthfulness of the population will also increase pressure on entry-level jobs. The Hispanic population will affect the West's health care system, economy, and political system. But the greatest impact may well be on the social fabric of the West, as formerly homogeneous states experience increasing ethnic diversity. Supporting data tables present total and Hispanic population figures, 1990 and 2000, for every county in the 11 states, covering four age groups: under 18, 18-34, 35-64, and over 64. (SV)