Your post doesn't say anything about what has been tried. Given that, I would get a crate and gate and go back to puppy 101. The dog shouldn't be allowed to just go potty anywhere in the house, because he shouldn't be anywhere in the house if he is unsupervised until he has earned it.

When there isn't someone to watch the dog, the dog is in the crate. When he goes potty outside, he gets tons of praise and a treat. When you see him going potty or getting ready to go potty in the house, you say no, pick him up, and take him outside to finish.

I think being in the shelter for so long (& his age) he just had to 'go' where he was confined. He has been caged, taken outdoors to do his business & then comes in & does it in his cage... or on the floor if out of his cage! Unfortunately, they live on 5 acres unfenced in the country where there are rattlesnakes, & rabbits that he would chase & get lost so he is on a leash when outdoors most of the time. He is praised when he potties outdoors but it doesn't seem to register yet.. but they have had him only about 4 months x the shelter so hopefully he will improve with time & patience. When he is visitung our 4 dogs he sees where they go but he will just do it anywhere-cement patio usually- when he feels the urge! Such a sweet lovable old guy though otherwise! We have never had chihuahas & some tell us they are very stubborn but our 3 Min-Pins learn things quickly (too quickly at times!!)& also our German Shepherds ... we have had 7 of them over the years.

Thanks for your suggestions!

Is he walked? I ask because in both of your posts here you said that you 'take him out' but did not say he is walked. Most dogs need to get moving before they eliminate. If you make sure he's empty before you bring him back into the house he won't pee in the house. Empty means that he may need to pee twice or three time. I've noticed that folks with smaller dogs often simply don't train the dogs as accidents are incidental. These dogs can surely be housetrained. It just takes vigilence and consistency. Cori's note is spot on - back to basics!

Cynthia: At home in the country my nephew's wife walks him daily outdoors on the 5 acres on a leash. When he visits us in the city, he runs loose all day as we have a huge fenced in yard & four dogs of our own (3 Min-Pins & a German Shepherd)to play with & wear the little old guy out! Even at our place he does not potty where the others go but just when & where the urge happens I think!

He is so lovable so I hope with ideas here that he can be trained. Our local Shelters do such a good job trying to find homes for all these abandoned animals. Now over-flowing & out of room for cats, they are having cats 'two for the price of one' now- trying to find them homes. They neuter,vaccinate,chip the adopted dogs for $40 usually & even less for low income, older persons.

Will pass this info. on to my nephew & wife to try with 'Paco'.... thanks!

I think Cynthia meant: is he walked each time he's taken out to do his business? They're not staying out long enough with him, and not moving around enough, if he comes in and does more.

Chi's can be a little more difficult to housetrain than other breeds but it's possible and will take patience with a guy that's older. My guess is he's never had any housetraining.

Maybe you have to treat him alike you would a puppy, keep him crated when you can't watch him. Take him out every 2 hours and send it out with the others. My 2nd dog was so easy to train because he went out with the older one.