I've heard from time to time that MLB clubs will workout some players at their parks before the draft. Does anyone know what determines who they invite to a workout and how many players generally get an invite? How many of the invites usually get drafted?

The pre draft tryouts I attended with my son had one to two dozen players, rarely did I see the same players at each try out. I know of 4 players who I saw try out that were drafted.
Shame OPP and Bighit15 dont post any more, they had alot of experence in the draft

Typically invited by the Scouting Supervisor as a show and tell sort of speak in front of GM and other front office brass.

Under most circumstances, pre-draft looks at the parent clubs parks in late May are drafted. In most cases they are closed door type workouts!

Regards
Bear

The predraft workouts are an exciting time. For most, its the first time you get to see your player hitting in a big league park. It's fun to see players from around the country work out, some with "national" reputations. At every workout my son attended, he knew a number of players, whether the workout was on the east coast or the west coast. It's amazing how small a world the baseball community is.
I would say most players got drafted by somebody, but of course not all get signed.(High school players)
Some players get notified early that teams would like to have them work out, others are lucky to get notified a week in advance. Usually their area scout will notify them. Some teams will actually pay for a player's expenses, some will pay expenses only if they draft & sign your player and others won't pay for any expenses.
Workouts are are held within a short period of time, causing scheduling problems because it's not unusual to have 2 or more clubs have workouts on the same day. The number of players that attended varied with as few as 10 to 30. My son and I had a great time during these workouts. It was a "senior trip" he will never forget. Good luck to all.

Something to be aware of:

some state HS federations do not permit such workouts while the HS season is in progress-- just a few years back a team had to foreit in the playoffs here in CT because of a player attending such a workout while the playoffs were happening.

Teams required a letter from the high school giving the player permission to attend work out

KO Promo,

I guess everyone's situation is different as my son was out of a JuCo, but he attended 3 pre-draft workouts in 2004. All of the invites came from the area scouts, but the GM's, Scouting Director and National cross-checkers for the respective clubs were in attendance at all three. There were not more than 30 players at 2 of the workouts and one of the workouts there were about 20 players.

He was fortunate enough to be drafted by a club that has some great people and he is very happy and looking forward to taking his shot.

Orioles42