We extend Hoggar's theorem that the sum of two independentdiscrete-valued log-concave random variables is itself log-concave. Weintroduce conditions under which the result still holds for dependentvariables. We argue that these conditions are natural by giving someapplications. Firstly, we use our main theorem to give simple proofsof the log-concavity of the Stirling numbers of the second kind and ofthe Eulerian numbers.Secondly, we prove results concerning the log-concavityof the sum of independent (not necessarily log-concave) randomvariables.