We study numerically the properties of solutions of spatially homogene
ous Bianchi-type IX cosmological models in the Jordan-Brans-Dicke theo
ry of gravitation. Solutions are obtained in which the scale factors u
ndergo irregular oscillations. The estimate of the maximum Lyapunov ex
ponent is found to be positive in the cases studied. These results see
m to be the first pieces of evidence in the literature of chaotic beha
viour in Jordan-Brans-Dicke cosmology. The range of values of the Jord
an-Brans-Dicke coupling parameter considered is (-500, -1).