There are any number of reasons why your cat might cry out at night. It's a mournful sound, you'd think their world was coming to an end ! In my house there is day time crying from Rueben who at nearly 18 is probably suffering old cat syndrome so is looking for reassurance. At night he cries as well especially when he is first put out to bed in the special cat quarters we call 'Pussy Hilton'. After a while he settles down but I've found it's best to try and ignore it otherwise he wails even more. Youngest cat Fergus will also cry a bit, plaintive little pips and cries as if we've totally abandoned him. Sometimes I tell him to be quiet in a firm voice which he generally obeys surprisingly enough. Understanding why they cry is the key to finding a solution especially at night, I mean who wants to have sleepless nights because kitty is upset and crying. This article might help to explain the possible causes.