It all depends on what you are passing from SSRS to the stored procedure (which is different that what is passed if you are using straight SQL in SSRS... if you are not using stored procedures, SSRS handles the parsing). For instance, say you are allowing the report users to select physicians in a parameter, and they are allowed to select multiple physicians for their report. The parameter values gets passed as follows:

"Dr. Smith, Dr. Jones, Dr. Dave"

all as a single string. The I noted in the Stored Procedure that the delimiter function actually parses the values into:

Dr. Smith

Dr. Jones

Dr. Dave

Be sure though, that when you add the parameter to the stored procedure it says:

Parameters!pLookupType.Value

and

NOT Parameters!pLookupType.Value(0) -- this instance will only grab the 1st value in the parameter array.