This study compares employer unemployment insurance (UI) tax costs and worker UI benefits across the 28 largest industrial states for 1988. The comparison is done using a detailed computerized micro-simulation model which computes the worker UI benefits and employer UI taxes for each state. Assumed characteristics of employers and employees are held constant across the states so that differences in UI costs and benefits among the states can be attributed entirely to differences in UI statutes. The principal findings of this study are: (1) the UI system can be modeled fruitfully at the firm level, (2) there are significant UI tax differentials across states attributable to statutory provisions, (3) UI tax differentials vary by type of employer, and (4) there is at least one significant regional difference: UI taxes are generally lower in Southern states.