Diapers adapted for use in the collection of stool samples from infants are disclosed. Such diapers may include a backsheet comprising an effectively liquid impermeable material, a transverse perineal barrier comprising an effectively liquid impermeable material and sealingly connected to another component of the diaper, and a liquid control structure disposed over the backsheet and forward of the transverse perineal barrier. The diaper may include other features adapted to contain exudates, isolate urine from fecal material following discharge, avoid absorption of liquid components of fecal material and enhance likelihood of collecting a fecal sample that is sufficiently representative of its composition immediately following discharge.