Path analysis is a methodology able of splitting the correlation coefficients into direct and indirect effects, helping the breeder in the study of quantitative traits. This study aimed to use path analysis to quantify such effects on the yield of theoretical ethanol, exerted by the variables total and culm dry matter yield, soluble solids content at harvest and efficiency of broth extraction, and on culm yield, by the agronomic variables average plant height at harvest, number of days until flowering, green matter yield and percentage of culms in the green matter yield. The soluble solids content variable presented the greatest total (0.8844) and direct (0.5969) effects on the yield of theoretical ethanol, indicating a great dependence of the main variable by the explanatory variable. The largest indirect effect was via culm yield (0.2820). The four variables considered as dependent (average plant height, number of days until flowering, percentage of culms in the yield of green matter and green matter yield) showed positive values for the total effect on culm yield. The largest direct effect (0.8010) was exerted by the green matter yield.