A meta-analysis combines analysis results from multiple independent sets of data. Metaanalyses to assess whether a treatment affects the occurrence of a medical event are frequently based on published aggregate data from controlled clinical trials. In that setting, the number of patients with an event in each trial is often treated as a binomial random variable. This assumes that censoring times have the same distribution in all treatment groups of a trial, and are independent of event times.To allow for different drop-out time distributions across treatment groups, we derive a likelihood for commonly available aggregate data that assumes specific event and drop-out time distributions for a number of situations. These include exponentially or Weibull distributed event and drop-out times, event-driven trials, the situation when a patient may experience multiple potentially fatal events, and when individual patient data are available for some trials.The assumption that parameters of survival distributions are exchangeable between trials is more plausible than for the expected proportion of patients with an event.For this reason the proposed likelihood is more suitable than a binomial likelihood for use in hierarchical meta-analysis models and for incorporating prior information from historical control group data. Hierarchical models and prior information are useful in sparse data settings and to avoid parameter identifiability problems. We use simulations to compare hierarchical Bayesian models with the proposed trial-level likelihood against other meta-analysis methods and to compare methods for using historical control group data. We also demonstrate how conjugate priors may be used to analyze exponentially distributed failure times without the need for Markov chain Monte Carlo methods.