AbstractA model was formulated and tested for the development of scientific reasoning abilities in adolescents. Piagetian theory provided the framework for choosing potential determinants of the dependent variable, scientific reasoning abilities. A model reflecting hypothesized causal relationships among determinants and with the dependent variable was developeda priorion the basis of theoretical and substantive reasoning. The hypothesized model was tested and revised using path analysis. Data from intact classes of middle‐school (n= 101) and high‐school (n= 89) students from an upper‐middle‐class suburb of a midwestern city revealed significant (p<0.05) path coefficients for these variables and scientific reasoning abilities: age, I.Q., field dependence–independence, and experience. A path from locus of control to scientific reasoning abilities through field dependence‐independence was also statistically significant. The revised model explained 61 percent of the variance in scientific reasonin