Pretty easy, but the heat can be oppressive and the bugs are irritating !

just finished trek -- will post review soon... essentially though, easy trek - 6 days waaay too long!
Mike

I thought, if they had reasonably healthy people the tour could be completed in 3 days. Our guides said they get there in 1 day when they are on their own.

yah.. posted a review above that the walking level was kinda lame-o.
3 days with 2 nights at the site would be pretty exhausting, but definitely doable -- 3 days to get there was just stupid.
If you do any trekking, definitely go for the loop.
Mike

i don't think 6 days is all that stupid as the extra time gave us the opportunity to interact with the locals where we camped
..break out the frisbee & they will come running...frisbee rules & the frisbyterian church is the one true religion..
If anyone suffers from respiratory problems, I'd be careful. The cots provided in Ciudad Perdida haven't been washed in years, so they're full of dust, mites, etc. Any asthmatic will surely have an attack. We had one in our group. He was fine walking, crossing the rivers, sleeping in hammocks, but said that the cots were "an immediate attack on the lungs", lol.
Other than that and the CONSTANT BUG BITES, it's not especially difficult.