The study examined those neighborhoods of Los Angeles County that had become high crime districts by reviewing specific conditions over the period 1950 to 1976. The onset of the transformation is most significant in understanding the creation of a high crime area. The pattern showed that as urban neighborhoods aged, they rapidly lost their higher income families. In their places came lower income single-parent families and higher income childless households. A decline in housing costs invited more lower income ethnic groups, who caused a changed neighborhood socioeconomic status. Orderliness in the use of public spaces declined, and new neighborhood standards of behavior supplanted the old. A subsequent invasion by offenders from the high crime areas caused an increase in property crimes. The crime rise occurred after single family dwellings gave way to apartment buildings, after more commercial and industrial complexes moved in, and after children and youth constituted an increased proportion of the population. Once the neighborhood started to develop into a high crime area, subsequent changes in population, occupancy habits, etc., mattered relatively little. The four indices of deterioration -- land use, demographics, socioeconomic status, and subculture -have the most effect at the beginning of the transformation and the least effect at the end. In terms of velocity of change, the most important of the four factors was a very high rate of change in socioeconomic status, followed by a moderately high rate of change in subculture. Five tables and six figures are included.