In this paper we examine the dynamics of suicide attacks and targeted killings in the Second Intifada. We find evidence that the targeted killings of Palestinian leaders by Israel reduce realized Palestinian violence. We find, however, that intended Palestinian violence is increasing at low levels of targeted killings, but decreasing at higher levels. We find that suicide bombings that kill at least one Israeli lead to a subsequent increase in the incidence and levels of Palestinian fatalities. Our results do not support the notion that suicide attacks and targeted killings follow the "tit-for-tat" pattern that is commonly postulated in the literature.Keywords: suicide terrorism, targeted killings, assassinations, Second Intifada, Palestinians, Israel 1 Unlike a conventional war involving ground or air combat on a battlefield between nation-states with armies of (roughly) equal capacity fighting to claim territory, several recent conflicts have taken place in populated civilian areas between groups with substantial differences in military capacity. These conflicts may include targeted killings (assassinations) of specific leaders on one side and suicide attacks on other -policies primarily designed to incapacitate or demoralize the opponent rather than to directly claim territory. In both cases, civilians are either deliberately targeted (as with suicide attacks) or are likely to be killed in the process (as with targeted killings). This kind of decentralized, somewhat sporadic, and clearly psychologically oriented warfare may be one of the defining characteristics of many of the conflicts of the 21st century.In the long-standing conflict between the Palestinians and Israel, the Second Intifada has been characterized by the increased use of suicide attacks by the Palestinians and an increased number of Israeli targeted killings of Palestinian militants of all ranks. Nearly half of the over 1,000 Israeli fatalities in the Second Intifada have been caused by suicide attacks, while about 8 percent of more than 4,100 Palestinian fatalities have occurred during targeted killings. Of these, nearly 40 percent were not the targeted individual(s).1 While neither of these tactics was introduced during the Second Intifada, 2 their heightened prevalence has resulted in their being perceived as the defining characteristics of the conflict. Palestinian violence increases when one moves from zero to one or two targeted killings per month, but then decreases at higher levels.In the next section we discuss the previous literature on suicide terrorism and targeted killings. We then briefly discuss our empirical approach. In Section III we describe our data on violence and intended violence. In Section IV we discuss the prevalence of suicide attacks among overall Israeli fatalities and the prevalence of targeted killings among all Palestinian fatalities. In Section V, we estimate the Israeli reaction to realized and intended suicide attacks by the Palestinians. We examine realized Palestinian reactions to targeted killings...