Electronic Journal of Differential Equations, Vol. 2011 (2011), No. 76, pp. 1-25. Title: A linear first-order hyperbolic equation with discontinuous coefficient: distributional shadows and propagation of singularities Author: Hideo Deguchi (Univ. of Toyama, Japan) Abstract: It is well-known that distributional solutions to the Cauchy problem for $u_t + (b(t,x)u)_{x} = 0$ with $b(t,x) = 2H(x-t)$, where H is the Heaviside function, are non-unique. However, it has a unique generalized solution in the sense of Colombeau. The relationship between its generalized solutions and distributional solutions is established. Moreover, the propagation of singularities is studied. Submitted January 19, 2011. Published June 16, 2011. Math Subject Classifications: 46F30, 35L03, 35A21. Key Words: First-order hyperbolic equation; discontinuous coefficient; generalized solutions.