The effectiveness of telephone crisis services/hotlines, examining proximal outcomes as measured by changes in callers' crisis state from the beginning to the end of their calls to eight centers in the U.S. and intermediate outcomes within 3 weeks of their calls, was evaluated. Between March 2003 and July 2004, 1,617 crisis callers were assessed during their calls and 801 (49.5%) participated in the followup assessment. Significant decreases in callers' crisis states and hopelessness were found during the course of the telephone session, with continuing decreases in crisis states and hopelessness in the following weeks. A majority of callers were provided with referrals and/or plans of actions for their concerns and approximately one third of those provided with mental health referrals had followed up with the referral by the time of the follow-up assessment. While crisis service staff coded these callers as nonsuicidal, at follow-up nearly 12% of them reported having suicidal thoughts either during or since their call to the center. The need to conduct suicide risk assessments with crisis callers and to identify strategies to improve referral follow-up is highlighted. (Contains 5 tables.) [For part 2, see EJ785871.]