Document And Entity Information - shares	9 Months Ended
	Jun. 30, 2020	Aug. 07, 2020
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Registrant Name	BIOANALYTICAL SYSTEMS INC
Entity Current Reporting Status	Yes
Entity Central Index Key	0000720154
Current Fiscal Year End Date	--09-30
Entity Filer Category	Non-accelerated Filer
Trading Symbol	BASi
Entity Common Stock, Shares Outstanding		10,989,066
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
Entity Interactive Data Current	Yes