Postdoctoral scholars may be economic complements or substitutes for faculty, doctoral research assistants and capital in the production of university life science research. Using data on 120 US universities, we present two cross-sectional (1993 and 2006) descriptive econometric models. Results suggest that postdocs serve primarily as complements to other labour inputs and capital. These relationships are potentially a source of concern to science policy makers because misperception and misallocation of complementary inputs is more costly than that of substitute inputs and may result in fragile and unstable systems. This instability is costly for individuals in the scientific workforce and poses a threat to the continued productivity and innovation of academic research.