Duncan's 1972 instrument was completed by 118 Project Managers to investigate perceived environmental uncertainty (PEU). Factor analysis indicates significant loadings on three factors corresponding to Milliken 's (1987) state, effect, and response uncertainty. Measures of project manager performance were found to be differentially associ-ated with total PEU and its disaggregated components of state, effect, and response uncertainty.

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This article proposes a new thesis about the role of individual differences in managers' media choice behavior. It argues that individual differences influence media choice only under conditions of low message equivocality. When equivocality is high, a “richness imperative” masks the influence of individual differences. Managers are compelled to use richer media to match the equivocality of the message. However, in low-equivocality situations, richness demands are lowered. Any medium is capable of carrying the message. Thus managers have more freedom to act on their preferences, and individual differences are more likely to influence behavior. The findings of an exploratory study provide some support for this theoretical notion. As hypothesized, the judging/perspective attitude, as measured by the Myers Briggs Type Indicator, influenced media choice under conditions of low equivocality but not under conditions of high equivocality. However, tolerance for ambiguity did not significantly influence media choice under either condition. Implications for future research and practicing managers are discussed.

R&D project managers work in an environment in which the uncertainty and complexity of engineering development problems are an important source of episodic job stress. A study of the US. Navy's top major project R&D managers (N = 118) was conducted to test the use of various coping skills and social support as preventive stress management techniques for this population. It was found that perceived environmental uncertainty (PEU) had a direct, positive effect on psychological distress of these project managers while social support had a therapeutic effect on their experience of burnout. While problem focussed coping had a small, positive effect on burnout, neither coping skills nor social support were found to have a primary prevention effect upon perceived environmental uncertainty (PEU).Engineering managers engaged in high technology R&D are confronted by a wide range of uncertainties, risks and changing demands that give rise to the stress response with its attendant physiological and psychological changes (Asterita, 1985). Adams (1980) has argued that an episodic versus chronic dichotomy of stressors is valuable because it distinguishes between intermittent stressors of finite duration (episodic) and ongoing stressors of indeterminant duration (chronic). This article reports the results of a study of uncertainty as an episodic work stressor for the U.S. Navy's high technology R&D project managers. The results suggest that R&D project managers should develop social support systems and structures to maintain well‐being and avert distress and strain.

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