In the paper the effects of individual and social factors on the performance of doctoral students (young researchers) in Slovenia are studied. The paper starts with an overview of theoretical models and empirical studies that originate in educational research and psychological research. The paper continues with a description of theoretical models and empirical studies that originate from organizational research and focus on explaining job performance. The Job Demands-Resources model (Xanthopoulou et al., 2007; Bakker and Demerouti, 2007) is used to explain why some doctoral students perform better than others. Social support networks and social support from a doctoral student’s research group (supervisor and co-workers) are operationalized as job resources. The proportion of explained variance of the doctoral students’ academic performance is 0.14. Social support and personal networks have the largest effect, following by work motivation.