Following leads by Maslow (1964, 1968) and others who described peak experiences, this study was designed to learn more about the (1) subjective effects; (2) after-effects; and (3) interpretations of intense positive and negative experiences. Comparisons were made between respondents' "most positive" and "most negative" experiences and between these positive experiences and those of members of a yoga ashram. It was found that except for the differences in affect, positive and negative experiences were similar in subjective effects and impact on later life. The most positive experience of most respondents fell short of peak experience as described by Maslow. On the other hand, the most positive experience of ashram respondents showed evidence of a genuine alternation of consciousness and lasting life change afterward. The results suggest that only in rare instances is therapeutic change or self-actualization initiated by peak experiences. Implications are discussed.