Spanish modal verbs may express necessity, obligation, probability, and possibility, in either their personal or impersonal modes. Analysis is based on examples of contemporary Madrid speech. Four modals, "poder,""deber (de)," tener que," and "haber que," are placed within a tripartite structure defined by semantic categories, "imminente" (imminent), "presumible" (presumed), and "precario" (uncertain). (GR)