VALENCIA, Spain, April 18, 2013 (AFP) - Dane Madsen carded five birdies and one bogey in his four under par 68 while Stal, a fellow graduate of the Challenge Tour, had four birdies in his bogey-free round.
Aguilar, 38, who won his only European Tour title five years ago, hit six birdies and two bogeys.
"This course is playing very nicely - especially in the morning with very little wind," said Aguilar.
"The conditions are absolutely fantastic. It's a very difficult golf course if you miss the fairways off the tee; as long as you keep it on the fairway off the tee you get pretty good chances. The greens are rolling really nicely."
Eight players were tied for fourth on three under while Sergio Garcia was among those round in level par.
Fellow Spaniard Miguel Angel Jimenez, in his first event of 2013 after breaking his leg skiing in December, carded a 76.
Leading and selected first round scores in the European Tour's Spanish Open on Thursday (GBR/IRL unless stated, par 72):
68 - Felipe Aguilar (CHI), Morten Orum Madsen (DEN), Gary Stal (FRA)
69 - Robert Jan Derksen (NED), Craig Lee, Joel Sjoholm (SWE), Daniel Brooks, Joakim Lagergren (SWE), Gonzalo Fdez-Castano (ESP), Matthew Southgate, David
Higgins
70 - Magnus A Carlsson (SWE), David Howell, Phillip Price, Simon Wakefield, Jose
Manuel Lara (ESP), Anthony Snobeck (FRA), Peter Uihlein (USA), Marc Warren,
Richard Finch, Eddie Pepperell, Edoardo Molinari (ITA)
71 - Alvaro Velasco (ESP), Lasse Jensen (DEN), Javier Colomo (ESP), Robert Coles,
Ricardo Santos (POR), Mikko Korhonen (FIN), Peter Lawrie, Peter Hedblom (SWE),
Carlos Aguilar (ESP), Alejandro Canizares (ESP), Nacho Elvira (ESP), Mark Tullo
(CHI), Paul Waring, Espen Kofstad (NOR), David Horsey, Justin Walters (RSA),
Pedro Oriol (ESP), Alexander Levy (FRA)
Selected:
72 - Sergio Garcia (ESP)
73 - Matthew Zions (AUS), Tjaart Van Der Walt (RSA) Richard Green
(AUS)
76 - Jose-Maria Olazabal
(ESP), Jbe Kruger (RSA), Miguel
Angel Jimenez (ESP)
77 - Andrew Dodt (AUS),
82 - Daniel Gaunt (AUS)