Researchers interested in studying the effects of subjects' reasoning levels, as defined by Piaget (Inhelder & Piaget, 1958), on science achievement or other dependent variables face two measurement problems. First, the traditional clinical method is time-consuming and impractical for large numbers of subjects. Second, alternative methods of assessment, although reliable and valid, may over- or underestimate subjects' reasoning levels. The objective of this investigation was to determine the effects of various methods and formats of administering a Piagetian task on subjects' performance. The task chosen for this investigation was the Mr. Short-Mr. Tall problem (Karplus & Lavatelli, 1969; Karplus et al., 1977). The task was presented using four methods: (1) individual clinical interview, (2) group presentation of task followed by paper-and-pencil problem with illustration, (3) group administration of paper-and-pencil instrument with illustration, and (4) group administration of paper-and-pencil instrument without illustration. Each method included four formats: (1) completion answer with essay justification, (2) completion answer with multiple-choice justification, (3) multiple-choice answer with essay justification, and (4) multiple-choice answer with multiple-choice justification. Three hundred seventy-six students who were enrolled in a freshman level biological science class participated in the study. The research design was a 4 × 4 factorial design with method and format of assessment as the main effects. The participants were in 16 distinct laboratory or discussion sections, and each section was randomly assigned to a cell in the research design. Regression analysis with the individual as the unit of analysis showed that neither method nor format of assessment accounted for a significant amount of variance in student performance. The overall interaction remained nonsignificant. Regression analysis with sections as the unit of analysis revealed similar findings. The inter-rater agreement in the scoring of the reasoning task was 98.4%. The principal conclusion is that neither method nor format of task administration influenced the performance of subjects, and this lack of influence is similar for various combinations of method and format. Discussion focused on the importance of this nonsignificant finding for using alternative methods of Piagetian assessment. Implications for teachers are also discussed.