Multiple sclerosis (MS) is associated with significant economic burden and high rates of unemployment. This investigation evaluated patient and disease characteristics associated with work loss and work initiation using the NARCOMS patient registry. Patient and disease characteristics associated with transitions to unemployment or employment were evaluated cross-sectionally and prospectively over the course of two assessment periods (mean interval of 1.56 +/- 0.93 years). Eligible participants included 8,867 patients for the cross-sectional component, and 8,122 for longitudinal analyses. At Time 1 and Time 2 56-58 % of MS patients were not employed. At Time 1, unemployed participants more likely to have a progressive disease course, had a longer symptom duration, greater levels of disability as measured by the PDDS, and greater functional limitations across all domains of the performance scales (p < 0.0001 for all). At Time 2, increasing MS symptoms in the past 6 months increased the odds of becoming unemployed. In addition, specific problems in mobility, hand function, fatigue, and cognitive performance domains were associated with increased odds of becoming unemployed. Less severe problems in similar areas, including mobility, hand function, and cognitive functioning were also predictive of work initiation among patients not employed. MS is associated with high rates of unemployment. Specific physical and mental health limitations confer risk of employment cessation over time, as well as the likelihood of employment initiation. This study has implications for rehabilitation interventions to target specific MS related limitations that place patients at greatest risk for work status changes.