The major purpose of this experiment was to examine the effects of format (bar graphs vs. tables) and organization (by year vs. by brand) on the speed and accuracy of extrapolation and interpolation with multiple, nonlinear trend displays. Fifty-six undergraduates enrolled in the College of Education at the University of Delaware served as the data source. Subjects were assigned randomly to four format groups, varying in trend direction (increasing, decreasing) and acceleration (low, moderate, high). Interpolation was relatively fast and accurate and was unaffected by experimental variables. Extrapolated values were overestimated with decreasing trends and underestimated with increasing trends; this effect was greatest with highly accelerated trends. Response time was lower, but accuracy unaffected, when data were clustered so that trends were perceptually salient. The format and organization of visual displays of quantitative data should be investigated further, since both seem to play an important role in extrapolation performance. (Author/KS)