L4 || align=right | 16 km || |-id=603 bgcolor=#E9E9E9 | 21603 || 1999 BY || — || January 17, 1999 || Catalina || CSS || — || align=right | 4.9 km || |-id=604 bgcolor=#d6d6d6 | 21604 || || — || January 19, 1999 || Višnjan Observatory || K. Korlević || KOR || align=right | 5.4 km || |-id=605 bgcolor=#d6d6d6 | 21605 Reynoso || || || February 12, 1999 || Socorro || LINEAR || — || align=right | 8.0 km || |-id=606 bgcolor=#fefefe | 21606 || || — || March 17, 1999 || Caussols || ODAS || — || align=right | 2.6 km || |-id=607 bgcolor=#E9E9E9 | 21607 Robel || || || April 6, 1999 || Socorro || LINEAR || — || align=right | 9.3 km || |-id=608 bgcolor=#fefefe | 21608 Gloyna || || || April 7, 1999 || Socorro || LINEAR || — || align=right | 3.0 km || |-id=609 bgcolor=#fefefe | 21609 Williamcaleb || || || May 10, 1999 || Socorro || LINEAR || slow || align=right | 4.4 km || |-id=610 bgcolor=#E9E9E9 | 21610 Rosengard || || || May 10, 1999 || Socorro || LINEAR || — || align=right | 8.1 km || |-id=611 bgcolor=#E9E9E9 | 21611 Rosoff || || || May 10, 1999 || Socorro || LINEAR || EUN || align=right | 4.4 km || |-id=612 bgcolor=#fefefe | 21612 Chelsagloria || || || May 10, 1999 || Socorro || LINEAR || V || align=right | 4.2 km || |-id=613 bgcolor=#fefefe | 21613 Schlecht || || || May 12, 1999 || Socorro || LINEAR || — || align=right | 3.2 km || |-id=614 bgcolor=#fefefe | 21614 Grochowski || || || May 10, 1999 || Socorro || LINEAR || — || align=right | 4.0 km || |-id=615 bgcolor=#fefefe | 21615 Guardamano || || || May 10, 1999 || Socorro || LINEAR || — || align=right | 1.8 km || |-id=616 bgcolor=#fefefe | 21616 Guhagilford || || || May 12, 1999 || Socorro || LINEAR || V || align=right | 2.6 km || |-id=617 bgcolor=#fefefe | 21617 Johnhagen || || || May 13, 1999 || Socorro || LINEAR || — || align=right | 3.1 km || |-id=618 bgcolor=#fefefe | 21618 Sheikh || || || May 13, 1999 || Socorro || LINEAR || — || align=right | 1.9 km || |-id=619 bgcolor=#fefefe | 21619 Johnshopkins || || || May 9, 1999 || Anderson Mesa || LONEOS || — || align=right |