ALTHOUGH THERE IS NO SINGLE DEFINITION OF TERRORISM, POLITICAL TERRORISM OR TRUE TERRORISM CONTAINS AT LEAST TWO ELEMENTS: AN ILLEGAL ACT OF VIOLENCE OR THREAT OF CRIMINAL VIOLENCE, AND A POLITICAL PURPOSE (AN ACT OF CRIMINAL VIOLENCE WITH THE INTENT OF CHANGING A GOVERNMENTAL POLICY). ALTHOUGH TERRORISM AND GUERRILLA WARFARE DIFFER, THERE ARE FEW RULES THAT CAN BE USED TO DRAW CLEAR DISTINCTIONS BETWEEN THEM. THEORETICAL OR ANALYTICAL DISTINCTIONS WOULD, HOWEVER, INCLUDE SEVERAL FACTORS. THE TERRORIST HAS AN URBAN FOCUS, OPERATES IN SMALL BANDS, AND INCLUDES, AS AN OBJECT OF ATTACK, THE PROPERTY AND PERSONS OF CIVILIANS. THE GUERRILLA'S FOCUS IS PRIMARILY RURAL; THE ORGANIZATION CAN BE LARGE; AND THE OBJECT OF ATTACK USUALLY INCLUDES THE MILITARY, POLICE, OR GOVERNMENT OFFICIALS. CONTRARY TO POPULAR BELIEF, THE NUMBER OF PERSONS ACTUALLY KILLED OR WOUNDED IN TERRORIST INCIDENTS IS LOW, COMPARED WITH DEATHS RESULTING FROM OTHER VIOLENT CAUSES. TERRORIST INCIDENTS, HOWEVER, HAVE BEEN ON THE RISE SINCE 1965, FROM 50 ANNUALLY IN 1968 TO 175 IN 1975. TERRORIST GROUPS INCLUDE THE ANARCHIST TERRORISTS; MOSCOW-ORIENTED COMMUNISTS; NATIONALIST GROUPS (SECTIONAL CHAUVINISTS); COMPOSITE AND ELECTIC GROUPS; MAOIST, PEKINGORIENTED SPLINTER GROUPS; BLACK RACISTS; NEW LEFT STUDENT-BASED MIDDLE-CLASS TERRORISTS; CASTROITE GROUPS; TROTSKYIST TERRORISTS; RIGHT WING REACTIONARIES; AND RELIGIOUS FANATICS. PREVALENT FORMS OF TERRORIST STRUGGLE HAVE BEEN VARIATIONS ON TWO MODELS--THE MARIGHELA MODEL OF URBAN TERRORISM OR THE GUEVARADEBRAY MODEL OF RURAL STRUGGLE. ALTHOUGH REPRESSION HAS BEEN THE USUAL RESPONSE OF NATION-STATES TO TERRORIST VIOLENCE, OTHER RESPONSES HAVE INCLUDED INFILTRATION OF TERRORIST GROUPS, ISSUANCE OF FINANCIAL REWARDS; CALL FOR ELECTIONS; AND TOUGH COUNTERTERRORISM LAWS. TERRORISM CONTINUES TO BE AN URGENT PROBLEM ON 5 CONTINENTS--THERE IS NO SINGLE TERRORIST MOTIVATION NOR UNIVERSAL RESPONSE. NOTES AND REFERENCES ARE APPENDED.