Box car competition: 9 a.m. to 3 p.m. Saturday, north end of Paiwa Road in Waikele. Open to all box cars that meet American Box Car Racing International standards. Call 947-3393.

Kahana Valley hike: John Cummings leads a trip through a wet, muddy valley that holds lush growth and opportunistic mosquitoes, Saturday. Five hours, 31/2 miles. Costs $5. Call the Hawai'i Nature Center at 955-0100.

Wa'ahila-Kolowalu hike: Zon Owen of the Hawaiian Trail & Mountain Club leads a ridge walk for novices, 9 a.m. Saturday. Costs $2. Call 597-8493.

La'ie hike: Ten miles on a graded ridge with Ken Suzuki of the Hawaiian Trail & Mountain Club, 8 a.m. Sunday. Costs $2. Call 845-4691.

Makiki Night Life: Bring the family for an evening adventure with Hawai'i Nature Center staff, 6:30 to 8 p.m. Sunday. Costs $5. Call 955-0100.

Zoo by Moonlight: Tour the Honolulu Zoo under a full moon, 7 to 9 p.m. daily, Monday through Sept. 26. Tickets $7 adults, $5 children; purchase in advance at cashier's booth. Call 971-7195.

Sports Acrobatics Hawaii: Hawaii Highflyers Trampoline Club for adults and kids, 4 and 5 p.m. Mondays and Wednesdays, McCully Recreation Center. Call Karl Vorwerk at 949-3747.

Waikiki Acrobatic Troupe meets 4 p.m. Sundays at the beach across Kapiolani Park Bandstand; free workout at UH Studio Four 8 p.m. Wednesdays. Call Don Heafner at 536-7205.

Learn to swim: Children practice Saturday mornings at Ala Moana Beach; adults, Monday, Wednesday and Thursday evenings. Free. Call the American Red Cross, 734-2101 ext. 123 or 124.

Free hike to Diamond Head: Meet the Clean Air Team at the Honolulu Zoo entrance, 9 a.m. Saturdays. Three miles to the top. Call 948-3299.

Philippine folk dancing: 2:30 to 4:30 p.m. Saturdays, Lanakila Gym. Free. Call 455-9963.

Hash House Harriers: Social runs with Aloha group 3 p.m. Saturdays; call 948-AHHH (948-2444). Or Honolulu group 5:30 p.m. Tuesdays; call 948-HASH (948-4274).

Hawaii Israeli Recreational Dance: Noon to 3 p.m. Sundays, Ala Wai Ballroom. Costs $3.50. Call 623-3603.

Honolulu Marathon Clinic: Free training runs with Jack Scaff and staff, 7:30 a.m. Sundays, Kapiolani Park Bandstand. Call Norm at 247-4957. No meetings on three-day weekends.

Ikebana classes Lillian Koide teaches flower arrangement 9 a.m. to noon Wednesdays at the Japanese Cultural Center. Tuition $30 per month plus supplies. Call 537-5765 evenings.

International folk dancing: Includes Bulgarian, Greek, Rumanian and Israeli dances, 7 to 9:15 p.m. Sundays, Makiki District Park. Donation. Call 923-0362.

Line dancing: 9:30 to 11 a.m. Tuesdays, Waikiki Community Center. Costs $3. Call 923-1802.

Scandinavian dancing: 7 to 9 p.m. Wednesdays, Ala Wai Golf Course Clubhouse. Free. Call 922-0793 or 955-2577.

Pali Twirlers square dance: 7:30 to 9:30 p.m. Thursdays, Yacht Club Terrace. Call 254-2333.

Honolulu Zoo: The zoo opens at 8 a.m. on the first and third Wednesdays of the month. General admission $6; $2 with Yum Yum Tree senior card. First Wednesdays feature a botanical tour at 8:45 a.m. for $2 more. Third Wednesdays, tai chi practice begins 8 a.m. Call 971-7174.

Nature Conservancy hikes: Two guided hikes a month to Honouliuli Preserve, home to more than 45 rare native plants and animals. Donation. Call 537-4508.