The high temperature pyrolysis of 1,3-butadiene has been investigated in the shock tube with two time-resolved diagnostic techniques: laser schlieren measurements of density gradient with 1, 2 , 4, and 5% C4Hs in Ar or Kr, 0.26 < Pa < 0.66 atm, over 1550-2200 K, and time-of-flight mass spectra for 3% C4H6-Ne, P, -0.4 atm, 1400-2000 K. When combined with a recent single-pulse shock tube product analysis covering 1050-2050 K, these measurements permit a complete modeling of major species in C4HI pyrolysis. Extrapolated density gradients and product analyses show initiation is dominated by C4H6 -2C2H,., significant falloff and Arrhenius curvature being seen in the derived rates. A restricted rotor. Gorin model RRKM fit to these rates with reasonable parameters generates