Despite suffering the flu, O'Toole, 22, of Newstead Harriers, put up a strong showing to top score in the shot and high jump for 3265 points, however Philpott, of North Launceston, had the upper hand in the 100m, long jump and 400m (50.99) to score 3453 points.
With day two traditionally O'Toole's strength, the result could come down to the wire in the final event of the competition, the 1500m today.
Hobart athletes currently fill the placings in the open women's event, with Sandy Bay's Jessica Lyden leading on 2665 from Wenonah Sharman on 2499 points.
Newstead Harriers' Brian Cooney and Aaron Humphrey from Hobart's Eastern Suburbs club are fighting out the under-20 event, with Humphrey currently leading by 99 points.
Hobart's Ben Rickards is in the lead in the tough under-16 boys' division from fellow Southerner Ryan Foster and promising new athlete Toby Campain, 14, (Newstead Harriers).
Brittany Knee (Western Suburbs) is the only competitor in the under-18 girls' and scored highly in her best event, the shot put (10.14m), to finish day one with 2025 points. Natalie Milne, 15, (Newstead Harriers) elected to compete in the under-16 age group and leads by almost 200 points from clubmates Ebony Hately and Daniela Weinreich.
About 50 competitors from took part yesterday.
A highlight of the day was a State shot put record set by Todd Hodgetts, of Newstead Harriers, in the under-18 boys' event.
The competition continues today at from 12.30pm with athletes trying to accumulate the required points to qualify for the junior national championships to be held in Canberra in March and the senior championships in Sydney in February.