Document And Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2018	Dec. 14, 2018	Mar. 31, 2018
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Registrant Name	BIOANALYTICAL SYSTEMS INC
Entity Central Index Key	0000720154
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 11,125,000
Trading Symbol	BASI
Entity Common Stock, Shares Outstanding		10,245,277
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	true