yes..we need more information ..how old is the baby? is there any medical problems? is he getting enough stimulation and attention during the day? babies that dont get enough attention during the day will get it at night.. if he/she is a newborn, it is only natural they are going to cry to be fed every 2hrs if breast fed and every four hours if bottle fed...is he/shes room too cold? to hot? wet diaper? you really havent given us much to go on
if your baby is between 14mos and 18 mos it could be separation anxiety..and therefor the 'Ferber Method" could be applied...it worked for my son in two nights..but its heartbreaking to hear your child cry..and theres nothing u can do about it... but prolonged crying is a sign something is wrong..
Good luck and feel free to message me personally with more information if you like..i could probably offer a little better advice if i knew more about the baby..age, sex, etc..

Hungry? Wet? Cold?

Don't newborns need a feeding every 2 hours?

My baby used to cry all night when she was still on the bottle and her formula had too much iron.The formula was giving her colic,once we figured out this problem,her formula was changed and that took care of the problem.

Here here some sites for you:

http://www.cbsnews.com/stories/2005/03/18/earlyshow/saturday/main681634.shtml

http://www.thenewparentsguide.com/babys-and-colic.htm

Other things it could be from personal experience:
he/she is--

overtired

allergic to formula or cereal (milk protein and soy are common allergies for infants)

Hope this helps

Is the baby teething? Try Hyland's Teething Tablets, available at Vitamin Cottage or health food stores. Does the baby get adequate time with primary caregivers? If not, the baby may be missing someone. My daughter was a very wakey baby. She's 8 now but at least she can tell me what's bothering her. You might try infant massage too. It worked wonders with my daughter.

It could be a variety of things.....Colic, hunger, needs to be changed, acid reflux etc. Does anything soothe the child? Perhaps swaddle baby if young enough...some chidren like that safe in the womb swaddling feeling?

I'm no pro when it comes to babies lol And it will be a few years prolly before i have my first. But just a suggestion.. Sometimes, babies tend to have the wrong sleeping schedule when compared to everyone else. Is your baby sleeping alot through the day? I had a cousin that i took care for a couple weeks. Her parents had her sleeping so much through the day that when it came time for the rest of us to go to bed, the baby was wide awake. I dunno if that'll solve your problem. But its some food for thought for all the other momma's and babysitters out there =]] Good luck

Since you're a mom I'm sure you know why babies cry and I assume you're asking because you have everything else covered. My nephew'd cry all night until the doctor discovered that the bottom of his esophagus was irritated because the gastric juices were burning it (due to the regurgitations). You should take your baby to the doctor