The IEEE Working Group on Voltage Stability is pleased to present its second special publication on the subject. Judging by the wide distribution of and referral to our first publication [90TH0358-2-PWR] has been one of the most comprehensive references on the subject that helped guide researchers and power system analysts in dealing with the phenomenon. At the time of its publication, there was noticeable disagreement on the definition and the dynamics of the phenomenon and how it relates to other forms of system instability. Although it did not answer all the questions, it helped focus discussions and activities around the crucial issues. Since then, a better understanding has been developed and specialized tools and analytical methods have evolved to the point where the Working Group feels timely to recommend a set of tools for voltage stability analysis ranging from the simplified conceptual analysis to the detailed long-term dynamic simulation.