How do you mean "divide" it? That suggests splitting the main stem and roots down the middle, which to me seems impractical. Maybe you mean how big a cutting can be taken from a large old Hoya plant.

You can't divide 1 plant in 2 like tropicbreezent said. However, you can root large piece by putting a heavy rock on top of the stem where you would like to cut but root them first because it's hard to root long huge cutting.

Thanks for all your comments... Actually, I have an huge Hoya that has 6 rooted stems in the same pot. It is becoming to big for my home. I was hoping I could repot it, but in 2 separate pots and at the end, having two smaller plants (as bc962 explained). I could give one and keep the other. I'd rather do that than start over a new small plant with cuttings... Sorry if my topic was not clear enough, I am a french speaking in an anglophone forum! Thanks for your comments bc962, I will try this, as it seams to have worked well for your Hoya!

I took some cuttings off of a friends Hoya that was about 25 years old. I potted them up in one pot. Here it is a few years later and i just propogated and separated them. All are doing well. Good Luck!

Just a word of caution... be gentle with the roots. Hoyas don't like to have their roots disturbed too much. I grow a lot of succulents and they can take a lot of root pruning and disturbance and it can actually promote new growth. Not Hoyas - they pout if you mess with their roots. So just don't be too surprised if it takes a bit for it to get growing after you do this. It just means its roots are getting settled into the new pot