At low latitudes under moderate to high solar conditions, a number of comparisons between the international reference ionosphere (IRI-90) model of F region electron density profiles and observed profiles measured by the Jicamarca incoherent scatter radar indicate that during the daytime the observed profile shape can be much broader in altitude than that specified by IRI-90, while at night, just after sunset, observed F2 peak altitudes are significantly higher than what is specified by IRI-90. Theoretically derived ionospheric parameters such as F2 peak density (NmF2), F2 peak altitude (hmF2), and profile shape, which are contained in the parametrized ionospheric model (PIM), have been shown in some cases to be in better agreement with Jicamarca observations. This paper describes a new low-latitude option for IRI-90 that uses five ionospheric parameters derived from PIM: the bottomside profile half thickness, NmF2, hmF2, and two parameters of a topside Chapman profile. The generation of electron density profiles using these five parameters is presented, as well as a description of how these parameters can be implemented into the IRI-90 model.¿ 1997 American Geophysical Union