"The evolution of fundamental concepts of occupational indecision–or career indecision–is initially summarized: dichotomous, developmental, cognitive, and multifactor concepts. Then, some typical evaluation tools that have enabled more fundamental research work on identity, intercultural differences, and the effects of guidance-related practices are presented. Finally, the evolution of fundamental concepts is mentioned through its possible avatar– uncertainty. Indecision, i.e., the inability of a person to make a choice when encouraged to do so, is an irritating state for the researcher who wishes to explain it, as it is for the expert who wishes to reduce it. Career indecision relates to the incapacity to make decisions about a major or a vocation. Career choices are worked out in two large frames of reference: family and school, the effects of which are pointed out. Various designs have been built, all of which cannot be set out: especially, strictly clinical approaches or those related to career decisions of adults engaged in the professional world. Indecision is often approached in a dichotomic–almost administrative–way, by the opposition of decided/undecided people. Studies on the frequency of indecision (lack of choice) and contrasts between decided/undecided adolescents turned out to be rather disappointing. Indeed, during adolescence, indecision often doesn't mean lack of career choice, but indicates a period of development of this choice. In the developmental approaches of decisions, some adolescents make choices rather quickly (and, therefore, are said to be decided) and others more slowly (and are said to be undecided). However, either quickly or slowly, some adolescents manage not to decide. Two forms have been distinguished: a developmental, normal indecision, and another form, more problematic and marked by a strong anxiety, chronic indecision. Undecided adolescents are thus not a homogeneous group: some are undecided and others indecisive and they undergo different processes. These processes have been studied within the framework of Cognitive Information Processing, where decision is considered as an application of several mechanisms, the dysfunction of the one being sufficient to create an undecided state. The location of these mechanisms is supposed to allow a reduction of indecision–which is not always true. Factors of indecision are indeed numerous and have been described in multifactorial approaches. A differential diagnosis of indecision is necessary for understanding the state of a person; this diagnosis makes it possible to assess the role of different factors (as lack of information or lack of decision method). These last approaches require precise data and adapted tools have been elaborated; some– among the most typical–are presented. With these tools, more fundamental problems have been examined as the question of identity, intercultural differences, and assessment of guidance practices. The assessment of these practices may be located among a body of research in France, from which one relates to college students: it is for an average indecision at the beginning of college ("university") that the later examination grades are highest. The idea of optimum indecision is then taken up in a more general way: depending on situations, an amount of indecision is adaptive and the current evolution of the professional world seems to indicate that indecision–which becomes a perceived uncertainty– could increasingly become more efficient because it leaves the person free to adapt to the modifications of the world."