<ul data-eligibleForWebStory="true">Diffusion models have been instrumental in generative modeling advancements.Even though current models generate high-quality average samples, individual samples may be of low quality.Detecting low-quality samples without human intervention is still a complex task.A Bayesian framework is proposed to estimate generative uncertainty of synthetic samples.The framework aims to make Bayesian inference practical for large generative models.A new semantic likelihood is introduced to handle challenges in high-dimensional sample spaces.Experiments demonstrate that the proposed generative uncertainty method effectively identifies poor samples.The Bayesian framework can be applied post-hoc to pretrained diffusion models using the Laplace approximation.Simple yet effective techniques are suggested to reduce computational overhead during sampling.