Avalanche dynamics has been described in organotypic cultures and acute slices from rat cortex. Its distinctive feature is a statistical distribution of avalanche size and duration following a power law with specific exponents, corresponding to near-critical state. We asked whether the same dynamics is present in dissociated cultures from rat embryos, which are characterized by complete lack of anatomic structure and high, random synaptic connectivity. We indeed observed such dynamics in some, but not all, experimental preparations. We conclude that the variability found in the dynamics of dissociated cultures also affects general features like the criticality of avalanche behavior.