Many urban theorists, notably W.J. Wilson, hypothesize that rates of male joblessness in low-income, urban neighborhoods have increased since the 1960s. No comprehensive study examines this claim, and case studies that consider it do not adjust for changes in school enrollment rates and size of the old-age population. This paper tabulates male employment trends in census tracts in 49 metropolitan areas from 1950-90 and models causes of these trends. Results show a marked decline in the employment of working-age men in low-income black tracts, both in absolute terms and relative to the employment rates of male residents of other types of tracts. By 1990, over 40 percent of working-age black men in low-income tracts were unemployed, about two-thirds of whom were adults between 25 and 64 years of age. This concentrated joblessness creates an environment that isolates residents from employed role models and job networks and worsens their opportunities for employment. Models indicate that declining urban manufacturing employment contributed to the declining employment rates for black men in low-income neighborhoods, but they do not support explanations based on spatial mismatch, suburbanization, or black out-migration. The paper concludes that Wilson is right to emphasize the employment problem of low-income black neighborhoods, and that black male joblessness in low-income neighborhoods in 1990 reached crisis levels. (Contains 55 references.) (Author/SM)