1999–2000 Tamil Nadu Legislative Assembly by-elections
Introduction '''By-elections''' to Natham and Thiruvattar constituencies were held in Tamil Nadu, India, on 5 and 11 September 1999 respectively. Elections for three state assembly constituencies, Nellikuppam, Tiruchirappalli - II and Arantangi  were held on 17 February 2000.In the first phase, TMC lost a seat to AIADMK and Dravida Munnetra Kazhagam (DMK) lost a seat to Communist Party of India (Marxist) (CPI (M)). In the second phase, AIADMK splinter party MADMK, was able to pick up a seat from AIADMK and DMK was able to hold on to its seats.
Results DMK+SEATSADMK+SEATSTMC+SEATSOTHERSSEATSDMK172 (-1)AIADMK4TMC38 (-1)CPI8BJP1PMK4CPM2 (+1)MADMK1 (+1)INC0FBL1MDMK0JD1JP1IND1TOTAL (2000)174TOTAL (2000)8TOTAL (2000)38TOTAL (2000)14TOTAL (1996)221TOTAL (1996)8TOTAL (1996)n/aTOTAL (1996)5* The number on the left, in the table, represents the total number of MLAs after the by-election, and the number in parentheses represents the seats picked up or lost due to the by-election* The numbers presented for 1996, represents, the alliance, when the TMC and the left allied with the DMK.
Constituents and results Source: Election Commission of India===Natham===   ===Thiruvattar===Source: Tamil Nadu Legislative Assembly   ===Nellikuppam===   ===Tiruchirappalli - II===   ===Arantangi===
See also 1.ECI By-election page
References